I am looking for an SQL Server E-book which starts from "What is a Database?"

 

Don't know if you're going to find anything that basic.

This was the first hit in a Bing search:
https://www.bing.com/ck/a?!&&p=dcb1...obmljYWxFLWJvb2tzZXJpZXMtZWJvb2suaHRtbA&ntb=1

I had to give them personal information to be able to access the three e-books they were offering:

 

I can see one here: https://riptutorial.com/ebook/sql-server
Looks detailed.