A simple sentence has 2 main clauses?
This is a simple sentence. Ben ate his dinner at 8pm.
This is a simple sentence Ben woke up early, but Sarah woke up late.
This is a compound sentence. Joel never studied, so he failed his exam.
A complex sentence has 2 main clauses.
This is a complex sentence. After he finished the essay, he noticed the errors.
This is a compound sentence. As he felt unwell, Harry went home.
This is a compound sentence. Harry loves football, but Paul loves rugby.
This is a simple sentence. Harry and Paul both love pizza.
This is a simple sentence. Harry loves diving and snorkelling.
This is a complex sentence. Steven, who was late for the meeting, was feeling very stressed.
This is a compound sentence. As the teacher shouted, the class went quiet.