Something that can be very confusing is the terminology agents and industry professionals use in the submission and query process. Many agents and editors ask for different things so how do you know what is what?
One or two sentences on how your book is different from other books on the shelf and in your genre.
A detailed description of the plot points and the ending.
One to three lines that describe your book in a sales-y way. How are you going to tell what your book is about, sell your book, attract attention, and stand out? It is a focused angle introducing the heart, high stakes and conflict of the story.
A combination of these things (one paragraph introduction/hook including genre and word count, one paragraph pitch, one paragraph author bio) including contact information so we know how to get ahold of you.
Prepare a one paragraph pitch, one page synopsis and three page synopsis to have on hand for whenever an agent or editor asks. Having this done ahead of time makes you look prepared and professional.