What are subqueries in SQL?

Question

Help me understand what is a subquery. In SL I find no such difference

Answer 1

A subquery is used to return data that will be used in the main query as a condition to further restrict the data to be retrieved. Subquery is a query inside a main query. Subqueries can be used with the SELECT, INSERT, UPDATE, and DELETE statements along with the operators like =, <, >, >=, <=, IN, BETWEEN, etc.

https://www.sololearn.com/learn/SQL/1861/?ref=app