when Magento will use catalog product flat table

I have not enabled the Use Flat Catalog Category and Use Flat Catalog Product in the admin panel. But when I checked the Database Magento created the flat tables.

Can you please give me a brief on the below things (if possible examples)?

1. What is a Flat Catalog?
2. When it will create Flat Tables?
3. How Magento will use this Flat Table (EAV V/s Flat) even though the flat option is not enabled?