Subject teacher question

Do you have a question for me? from the topic just treated in week 1 (salt).

Please can you explain complex salt more

A complex salt is a salt that contains one or more complex ions—ions with metal centers and different molecules attached. In chemistry, a salt is any compound composed of oppositely charged ions. These ions are negative (called anions) and positive (called cations), resulting in a charge of zero.

Can you explain more on double salts and complex salts and their examples, similarities (If any) and their differences