A diesel locomotive is one that uses a diesel engine as the prime source of power to move and pull cars.
Diesel locomotives are very popular today and can be seen working on all continents (with the exception of Antarctica, where the railway network is rather scarce). Being powerful and not requiring additional technical infrastructure like their younger siblings — the electric locomotives — diesel engines are perfect for most types of tasks.
Diesel engines can pull passenger trains, boxcars with goods, tank cars, platform wagons with wood logs, you name it. If the conditions are tough or the load is too heavy for a single diesel locomotive, a pair of engines can be used. And sometimes you can even see three or four of them if the job is exceptionally demanding.
Most national and private railway companies nowadays own or lease a multitude of diesel engines. They range from small, nimble ones used for maneuvering at railway stations to large, bulky machines utilized for the cross-continental trail.
Diesel engines also come in all shapes and colors, making up a happy useful bunch.