A jamb (from French jambe, "leg"), in architecture, is the side-post or lining of a doorway or other aperture. The jambs of a window outside the frame are called “reveals.” Small shafts to doors and windows with caps and bases are known as “jamb-shafts”; when in the inside arris of the jamb of a window they are sometimes called "scoinsons."
A set door include door jamb and door casing
If you want to install a door in your house, you have to first frame the door opening to prepare it for the installation. With a ladder, some nails and a hammer, you're well on your way to outfitting your own rooms at a fraction of the cost.
There are virous types of the door frame, you can choose the flat one or the designed. According to your home style, buy the best situable for installing. You will like your home.