What is a “run-on” sentence?

From LitWiki

Run-on sentences

Run-on sentences, also known as "fused sentences", contain two independent clauses, either of which can stand by itself. When these two independent clauses are connected by a comma, it is known as a comma splice. When there is no comma, these clauses become harder to recognize. Another point about run-on sentences is that it really doesn't matter about the length of the sentence. A run-on can be a very short sentence, such as "Nothing is on t.v.,I should turn it off,". Just because a sentence is very long, though, it does not necessarily mean that it is a run-on. On one of the works I have cited below will have a like to a 239 word sentence.