This solution defines what a run-on sentence is, gives an example of one, and tells you how to fix it, again using examples.
Any grammatical sentence should be concise, and should typically contain only one main idea. A run-on sentence is a sentence that contains more than one main idea. For example:
When I went to school on Monday I took the bus and it dropped me off on the far side of campus, ...
A run-on sentence is modeled.