Throws are done by pressing the Throw button or 1 + 3. This normal throw is unblockable and puts your opponent behind you after the animation is done. If you hold forward then execute a throw, you will perform a forward throw which pushes your opponent further away from you, instead of going behind you like what a normal backward throw does. This is very integral in the corner game, as it allows you to keep your opponent stucked in a corner if you want to, or escape from the corner yourself if you are getting trapped already.
If you are able to press the Throw button at the exact same moment that your enemy throws you, you will be able to break or "tech" the throw.
Command throws are special moves that are considered as unblockable. Unlike normal throws however, they cannot be teched or escaped. This goes the same with Super Moves which are considered throws as well.