How to deal with a database diagram?

Question

MySQL

I watch video on mysql. We built a diagram, but something is not completely clear, or rather, it is not at all clear what and how it works.
You can explain on your fingers who contains what, and indeed the general logic.
books - books
users - buyers/users
store - warehouse
orders - orders

Answer 1

more precisely, it is not clear at all

Erase all those clips. Study something like this:
1) Connolly, Thomas M. & Begg, Carolyn E. Database Systems: A Practical Approach to Design, Implementation, and Management.
2) Kroenke, David M. & Auer, David J. Database Processing.

Answer 2

There is a Books table, it contains all information about books (title, author, number of pages, etc.) There
is a users table, which contains information about registered users on the site (name, phone number, etc.)
warehouses table, this table contains the warehouse number, the book and its price
Well, the orders table, which stores information about orders (it contains information about who ordered and what ordered)
Lines - links between tables (read about one-to-many , many-to-many, one-to-one)