is the international terminal different from north terminal

Yes

Yes.The North terminal is for domestic traveling and the International terminal is for international traveling.

Yes, they are different

There are two terminals, international to the east, and domestic to the west. All 7 concourses are easily accessible from either terminal, using the plane train. Therefore, it does not really matter which terminal you use. Edit: "North Terminal at ATL probably refers to the northern entrance of the domestic terminal.

OMG, just read the signs and your ticket, should tell you where to go