; is called 'semicolon'. Semicolons separate things. Most commonly, they separate two main clauses that are closely related to each other but could stand on their own as sentences if you wanted them to. e.g. "I have a big test tomorrow; I can't go out tonight." The two clauses in that sentence are separated by a semicolon and could be sentences on their own if you put a period between them instead: I have a big test tomorrow. I can't go out tonight. One reason you might choose to use a semicolon instead of a period is if you wanted to add variety to your sentence structure; for example, you might use a semicolon if you thought you had too many short, choppy sentences in a row. This article explains it more thoroughly; https://writing.wisc.edu/Handbook/Semicolons.html