A cadet is a trainee enrolled in a military academy. You might also call a cadet a plebe, but doesn't cadet sound so much better?
The term cadet has many meanings: the first meaning referred to a younger male in a family. That might help you remember that a cadet is someone young: specifically, a student in a military academy. In the United States, cadets are trainees at military colleges. The cadets get a college education while also training to be officers in the armed forces. Being a cadet is a blend of traditional education and military training.