The three main types of patio doors are hinged (French), sliding, and bifold.
Hinged patio doors swing inward or outward from the frame — side-by-side hinged patio doors that open or close toward the middle are called French doors.
Sliding patio doors operate by the same principles as sliding windows, just on a larger scale. Glass panels glide along upper and lower tracks built into the ceiling and floor, respectively.
Bifold patio doors operate like a fusion of the above, featuring glass panels that stack up on top of one another like an accordion as they're pulled along a track.