First, some vocabulary in case you need it:
A Logline gives the gist of your book in a sentence. It tells something about the main character, the conflict, and the stakes. So, the WHO, the WHAT, and the WHY of your story.
When someone asks you what your book is about, you’ll probably give them your logline.
A Tagline is a catchphrase that sucks the reader in. It’s the idea behind your book. AKA: the hook. It might be on the front cover of your book.
The tagline’s job is to evoke emotion.