A small C program running on the EV3 brick receives data from the PS3 SIXAXIS over Bluetooth HIDP and sends motor commands to the Mindstorms firmware using the EV3 TCP protocol. This offers richer control options than the stock IR remote and a more familiar user experience than Android/iOS-based remote controls.
In earlier approaches the gamepad would connect to a PC over Bluetooth or USB, and the PC would send commands to the EV3 brick over Bluetooth or WiFi. Here the gamepad connects directly to the EV3 brick. See http://www.pabr.org/bricks/brickhid/ for details.