A locomotive is a train car that provides the power for the entire train. Traditionally this car pulled the train from the front, but modern trains may have a locomotive at either the front or back -- or both, for extra power.

Even though modern electric and diesel trains actually use an airhorn rather than a whistle, that booming sound a train makes as it passes by is typically referred to as a whistle. Steam train conductors pull a cord to operate the whistle, while modern airhorns typically blow at the touch of a button.

A double-decker lounge cars carries passengers on two levels with the same footprint as a single-level car. Known as Superliner on Amtrak, these double-decker cars may be coaches, dining cars, lounges or equipped with sleeping berths.

Tank cars are special boxcars used to carry liquids or compressed gases. They may be used for anything from fuel to chemicals to liquid waste.

In the earliest days of the railroad, rails were held in place with cast iron or wooden wedges. Later, they were secured using cast iron spikes. The final spike used to complete a line or join two lines together is often referred to as a golden spike.

Back in the old days, railroad employees painstakingly laid thousands of miles of track by hand. Modern workers have it easy by comparison, using a track-laying machine -- also known as a track renewal train -- to remove ties and spikes, clean and replace the ballast and restore the ties.

A smokestack is an iconic piece of equipment found on classic steam trains. Also known as a funnel or chimney, the smokestack releases exhaust and prevents pressure buildup within the smokebox.

A spike is a classic piece of railroad equipment. Made from metal and with an offset head, spikes -- which are around 6 inches long -- secure the rails and plates to the wooden ties.

Move over steam and diesel -- electricity is a clean and viable source of energy for trains. Overhead wires and lines provide power to the train, and are themselves fed by feeder stations located along the route.

Rail ties, or sleepers, are the wooden beams installed between a pair of railroad tracks. They not only lend support to the rails and help keep the rails spaced properly, but also transfer the weight of the train over the ballast.

The control stand is where the locomotive engineer works. It is home to the controls used to operate the engine and brake the train, and is located within a car known as the control car.

The truck frame -- known as the bogie in parts of Europe -- is the structure underneath of the cars on the train. It not only provides structural support, but also acts as a form of suspension to control shocks.

A flat car is a type of railcar used to transport specialized loads. It's not enclosed like a boxcar, and is useful for oversized objects like machinery and vehicles.

A Jordan spreader is a simple piece of equipment that has been in use in the railroad industry for close to a century. This machine is pushed by a locomotive, and can be used for everything including spreading gravel, improving drainage and removing snow.

A centerbeam is a type of specialty railroad car. It's nearly entirely open, with a center partition that can be used to carry large cargo, such as bundled roofing, siding or lumber.

The standard doors on modern trains are air-powered, and slide neatly into place before the train leaves each station. It wasn't that long ago, however, that the doors were manually operated. These manual doors were sometimes known as slam doors.

A firebox is an important piece of equipment used on steam trains. Found in the locomotive, it's used to generate heat for the boiler, which produces the steam used to power the engine.

Trains have a single central headlight on the front of the locomotive. This light not only allows the conductor to see the tracks ahead, but can also warn anyone nearby that the train is rapidly approaching.

The coupler, or coupling, is the equipment used to connect train cars to one another at the front and back. These couplers are standardized so that many different types of cars can be used on a single train setup, though different designs are available.

Crossing gates are important safety devices found at many at-grade crossings. They consist of red and white striped bars that come down to prevent anyone from crossing the tracks until the train has safely passed. Many crossing gates are accompanied by safety lights, alarms and other additional means of warning that a train is approaching.

Today the windows on most trains are fixed for safety reasons. It wasn't that long ago that passengers could open the windows with ease, allowing them to wave goodbye to friends and family -- or let in unpleasant smoke and cinders.

A train is no car or truck. Rather than pressing the gas pedal to get moving, conductors use a piece of equipment called a throttle. The throttle has eight notches, with the highest notch numbers associated with the fastest speeds.

A fish plate is a metal bar used to join two separate rail lengths together. The plate is pressed against the side of the rail and fastened in place using bolts on either side, which pass through the web -- vertical portion -- of the rail itself.

A tamper is a large piece of railroad equipment used to tamp the ballast. The tamping process using hydraulic technology to level the ballast and force it under the rails and ties, ensuring there are no gaps or empty pockets.

Ditch lights are located on the front of the train down near the wheels. Requirements for ditch lights on U.S. trains were added in the '90s to improve railroad safety standards.

In railroad terminology, a frog is a structure used where two rails cross one another. It is built in such a way that the wheels of the train can safely pass from one set of tracks to the other. It's also known as a switch frog.

The caboose is the very last car on the train. It serves as a lookout station, a hangout space for crew and an office for the conductor. On some modern trains, the caboose simply serves as a housing for the braking system.

Train wheels are made of metal. They are pressed onto steel axles and mounted on the base of the train -- which is known as a truck. The wheels are subject to frequent maintenance, including truing, or keeping the wheels round and smooth.

An open-top hopper is a type of train car without a top. It's used to transport bulk or dry goods that are not affected by the weather -- like rocks or gravel. The hopper is loaded from the top, but emptied from the bottom once the train reaches its destination.

An undercutter is a powerful piece of equipment used to scoop several inches or a foot of ballast out of the railway at a time. The ballast is collected in a hopper for disposal, and then replaced with new stone for better drainage and support.

A spike setter sets the thousands of railroad spikes that hold the rails firmly in place. While these spikes were once set by hand, a spike setter makes it easier and safer to set the spike.

A railway switch guides train wheels from one set of tracks to another. A switch signal lets train conductors know whether to wait before switching, or whether it's safe to proceed.

Metal train wheels face a lot of abuse as they roll on down the tracks. A wheel lathe is a piece of equipment that smooths and shapes the wheels from below, which is much easier than trying to remove the wheels from the axles for maintenance.

It's hard to think of a more crucial piece of train equipment than the rail itself. Constructed from rolled steel, it's built in the shape of an asymmetrical I-beam, with the top narrower than the bottom. The earliest rails were wooden, but wore quickly, and were soon replaced with metal.

Connecting rods, also known as main rods, are different from coupling rods. They are used to convert the motion of a piston in the train into the power needed to make the drive wheels turn.

Not all wheels on a train are drive wheels -- or wheels powered to move the train. A coupling rod, or side rod, connects the drive wheels to the non-powered ones so that all the wheels can move in sync. All steam trains have coupling rods, though not all electric and diesel ones do, depending on their design.

A crossbuck is a traffic sign used around train tracks. It typically includes a black-and-white X-shaped sign marked "Railroad Crossing," and it may or may not be accompanied by other gates, bells, whistles and warning lights.

The boxcar is by far the most common type of car found in the railroad industry. Per its name, it consists of a large metal box that can be used to carry cargo, such as pallets or crates.

Railroad tracks are typically surrounded by a huge amount of gravel and crushed stone, which is called ballast. Ballast helps to distribute the weight of the rails and ties over a larger area, and also enables proper drainage for the railway.

Over time, the wooden ties on railroad tracks can become worn down and ineffective. While a few ties can be removed manually, a large-scale project goes much more quickly using a piece of equipment called a tie extractor. This machine pulls out the old ties without disturbing the rails, and can slide new ties into place if needed.