It gives you the ability to create invisible portals wherever you want. For example, someone could shoot you and you could create a portal in front of yourself that would be the entrance and have the exit be another portal that redirects the bullet back at the person. Initially, it you might have limited range and number of portals that you could make. With training, you might be able to create permanent portals on islands/wherever you want that you can port to.
A weakness (since you could just cover your body in portals or something) would be that when you make portals the have to be in pairs, with the entrance for one being the exit for the other, and vice versa. So if you had a portal covering the front of your body, if someone attacked through it's pair that you placed somewhere else, it would hit you. The user would need to tactically place them and know when to close the portals and how to control them effectively.
I guess it would kind of be like the portals in the game Portal lol, except you can make more than one and make them anywhere.
Portal Array: Create multiple close range portals in front of yourself and rapidly punch/attack through them, with the exits being directed at a large group or one individual.
Portal Prison: Lock someone between 2 portals.
Portal Fall: Force someone through a portal and have the exit be high in the sky, so they fall down to the ground.
Portal Redirect: Portal someones attack right back at them.
Portal Escape: Portal to a location where you have a portal created already (like another island/location)
Portal Blink: Dash through a portal in front of you and exit right in front of a foe.
Portal Punch/Jab/Kick/ect.: Attack through portal in close range to hit someone far away.
Portal Fly: Continually make portals through the sky, allowing you to fall from portal to portal to travel large distances. (So you create a portal, enter it and have the exit in the sky above you, fall and make another portal mid-air that would have the exit in the sky in the direction you want to go and continue this process...may take some training to master).