To drag something means to physically pull it, like when you drag your sofa to the other side of the living room in order to get a better view of the TV.
Drag can also mean to prolong something. In this case, drag is often followed by the words "out" or "on." You could describe a class that drags on for hours, or try to drag out your homework to get out of doing the dishes. You can also drag someone unwillingly into a discussion or other situation. Anything that's boring and tedious can also be called a drag — like lunches with your great aunt Martha or cleaning the bathroom.