Patrick S. answered 05/24/22
Experienced Yale graduate who tutors AP, ACT, SAT, SSAT, and Writing
Essentially, the semicolon is used to join two complete independent clauses whose information is related to create a compound sentence, as in "The Uber was late; we walked instead." Note, however, that you could also correctly say, "The Uber was late, so we walked." (comma and a conjunction = semicolon)
Or, you could say, "The Uber was late. We walked." (two separate sentences)
Or, you could create a sentence with a dependent clause, followed by a comma. followed by the main clause, as in: "Because the Uber was late, we walked."
Also note that in the last example, you discovered that your English teacher lied to you when he or she said you could not begin a sentence with the word "because." "Because" may begin a dependent adverbial clause with grace and dignity, as it just did. :)

Patrick S.
05/24/22