All doors no matter what type are fitted into door frames. A door frame is a lining usually made of wood that is fixed into a structural opening in a wall. It is impractical to fit a door directly to a brickwork wall and for that reason the door frame is essential. The door is fitted into the frame. The frame is then lined with wood linings or architraves of the same finish as the door. 

Frames are made from long lengths of molded timber and then cut up into smaller lengths to assemble the frame suitable for the door size. The profile of the framing depends on the location of the frame and the type of door that will be fitted. A frame used to hang an internal door would be quite different to a frame for hanging external hardwood doors for example. There are a couple of types of internal frames used. The first is a simple frame comprising square edge timber section. The frame is assembled to suit the size of the door and the door is hung on one side of the frame. Timber door stops are then planted onto the surface of the frame. The door closes against the stops and secured by the lock. The second type has a rebate cut into the frame. The door is hung into the rebate and in this instance no door stops are required as the rebate up stand does the same job.  » Read more: What Are Door Frames