A misaligned frame is a door frame that has distorted or moved from its original position, so that the door no longer fits properly: the gap around it is uneven, it rubs at some point or the bolt does not go straight into the strike plate.
It can come from settlement in the building, from damp swelling the timber, from loose fixings into the wall or from an attempt to lever the door open. With aluminium and uPVC it is sometimes down to the frame not being fitted plumb.
You can spot it by looking at the gap between the door and the frame: if it is wider at the top than at the bottom, or the door swings open or shut by itself to one side, something has moved. Sometimes it can be corrected by adjusting; other times the frame has to be refitted. More under door repair and adjustment.