When your trying to make a compound sentence you need a conjunction like and,but,so,or you can use semicolon.
But if you're writing with semicolons you don't need a conjunctions in it.
You have to know that a simple sentence and a compound sentence are tow different thing a compound sentence needs conjunctions in them and a simple sentence needs a capital letter,subject,verb,make,sense,puctuation .
So when your trying to figure out which one is which you now know that a compound sentence has to have a conjunction,a simple sentence has to have more things than a compound sentence.
For an example: James is hungry he wants to keep playing video games.James is hungry, but he wants to keep playing video games.
for another example:John playing basketball he likes playing tooJohn was playing basketball,and he like playing too.