To define the structure of an SQL database you use queries. That name is a bit strange for commands which tell a server to create things for you.
On the next few pages you will learn how to create a database, tables and fields. This is something you will only do occasionally. Once the database is there you can do interesting things with the data.
These database definition queries and the database manipulation queries which come soon are all you need to run Web sites. IN fact later on you will learn a way to do the definition stage without queries and you will not even need to remember those.