what is difference between Co-related sub query and nested sub query?

what is difference between Co-related sub query and nested sub query?

Co-related sub query is one in which inner query is evaluated only once and from that result outer
query is evaluated.
Nested query is one in which Inner query is evaluated for multiple times for getting one row of that
outer query.
ex. Query used with IN() clause is Co-related query.
Query used with = operator is Nested query