An exam is a test. Many high school and college classes have a midterm exam and a final exam.
The word exam is short for examination, from 19th century student slang. An exam usually takes place in a class and consists of questions that test a student's knowledge. Sometimes the word describes a medical test of some kind, like an eye exam, a dental exam, or a physical exam. Rather than testing knowledge or skill, these exams are procedures meant to diagnose or rule out illnesses.