What is run on error in grammar?

If your teacher writes as quickly as I do, you may have had a hard time reading some of the comment on your paper. I believe the error your teacher identified is a "run-on error." The very common run-on sentence error happens when one sentence or independent clause is placed immediately after another independent clause with NO punctuation of any kind. To correct: 1) Make two sentences 2) Join with a comma and 'FANBOYS' 3)Use a semicolon (;) 4) Make one clause a dependent clause by using a subordinating conjunction like 'because, although, after'