It depends on the age of the door and the circumstances of the 'Jam'.  If it's very old, the problem may be that the foundation of the building has settled and the doorway is no longer 'square'.  If the door is new, it may have swelled from moisture, and need to be lubricated with orange oil.  In any case, the circumstances need to be explained more fully, so that a cure can be found.  Almost always, the door needs to be opened, sometimes by brute force, and the fit adjusted, either by planing the door or by adjusting the opening.