The car at the head of the train is typically the locomotive or engine, which is responsible for pulling the train and providing power. It is usually located at the front to ensure proper control and visibility for the train driver.
If it's a powered locomotive, then a locomotive. If it's a car with a cab to control the train, then a cab-car. If it's a train powered by itself, called a Multiple Unit (MU) with the engine part of the train, the front is called, well, the head end.
The engine most of the times.
The front of a regular train is usually pulled by a locomotive. This is the powerhouse of the train. If your train doesn't have a locomotive, but looks like cars with a window for the train crew, then that can be called the cab car, or as you put it, "the head of a train". There isn't any slang (that I know of) used to call it something special. I uses "front of train", but "head" sounds better. We do shorten "locomotive" to just "loco".
There are generally 3 types of cars at the head of a atrain. The car at the head end of a train is most oftena locomotive, but it can also be a "cab car", which has a cabin for the train operator/motorman/engineer, but is not a locomotive. For many transit systems, this car may be a Multiple Unit (MU) or Electrified MU (EMU) car. In most cases, when a freight train is seen with a freight car at the head of the "train", under US law, this is most often not termed a train, but a "consist" - this is because it fails to have the markers necessary to move legally as a train.
The front of a regular train is usually pulled by a locomotive. This is the powerhouse of the train. If your train doesn't have a locomotive, but looks like cars with a window for the train crew, then that can be called the cab car, or as you put it, "the head of a train". There isn't any slang (that I know of) used to call it something special. I uses "front of train", but "head" sounds better. We do shorten "locomotive" to just "loco".
Each part of a train is called a car.
Conventionally it's the locomotive, but it may just be a control car, or a car with a control cab.
The "Engine".
The caboose
Normally that would be the locomotive, but it might be a control car (push-pull trains), or a snow plow.
caboose