Size : Shows the size of the HTML used on your site.
Compressed Size : This is the size of the HTML on your site once it has been compressed.
Information : Page Speed is the speed at which your site responds to commands input.
It is more important and beneficial for your site to have this at a lower value.
Domain is either you or your company's ID in the Internet, when you apply to connect to Internet, they will give you protocol number. Every device connected to Internet has an IP number.