What is HTTP and socket in opera mini and what is the difference between them? What is the HTTP and socket option in android version of opera mini?
There is two options: HTTP and Socket/HTTP

The default is HTTP and Socket/HTTP.
In addition what is the different between these two options?
The socket connection keeps the connection to the sites. The HTTP selection will search for the site, each time searching for the site's IP address.

If you can't get a connection through the socket then switch to HTTP.
This choice is available when you’re using extreme-savings mode; use the "O" button and go to the savings summary.

The Socket/HTTP browser setting is faster and more cost efficient,
whereas HTTP is a fallback when your operator does not support socket/HTTP.