Locomotive classifications categorize trains based on their design and function. Common systems include the Whyte notation, which uses a series of numbers to describe the wheel arrangement, such as 4-8-4, indicating four leading wheels, eight driving wheels, and four trailing wheels. Another system is the UIC classification, which employs a similar format but includes letters to denote specific features. Additionally, locomotives can be classified by their power source, such as steam, diesel, or electric. Each type has unique characteristics and applications, influencing their use in freight or passenger services. Understanding these classifications helps in identifying the capabilities and historical significance of different locomotives.