A run-on sentence is a sentence that is wrong because it is too long.
It does not make sense without a period in the middle.
Run-on sentences should be two sentences.
We need to divide run-on sentences into two or more sentences.
The sky is blue it is full of clouds.
The sky is blue. It is full of clouds.
I have good ideas I can't put them into a sentence.
I have good ideas. I can't put them into a sentence.
She put on sunscreen the sun was extremely hot.
She put on sunscreen. The sun was extremely hot.