How do you know if a sentence is a fragment or run-on

A run on sentence usually consist of too many ideas in one sentence that goes on where there should be a period instead.

ex. I am going to a party in my hometown we are going to have fun.

A fragment on the other hand is a incomplete sentence. It doesn't make a correct and complete statement.

I met. or She was.

please vote my answer brainliest. thanks!!

Question 4 i think is expository