About the difference of mail add-on and mail hosting?

About the difference of mail add-on and mail hosting?

Hello,

1. Are Zoho mail add-on and zoho mail-hosting different things? Or same thing?

2. Should I purchase them separately ?

3. When I subscribe to Zoho CRM, I have choosen zoho mail add-on ? Do I need to purchase Zoho mail hosting?

4. Do I need to purchase mail hosting from the registrar where I purchased my domain?

Thank's
Zorge