4 of 5 Edited the title to match the same name as in the body of the post, added the bagavata-purana tag

What is the difference between Shrimad Bhagavatam and Bhagavad Gita?

Is Bhagavad Gita tells about one avatar and Shrimad Bhagavatam tells about all the Avatars?

Are they equivalent to each other or both are different?

Which is first written? And when and why the later one is written if both are same?

Are both of the same author or different books?