A lipogram is a poem written with some kind of restraint. Here is mine, using only the left side of my keyboard (except the comma, I had to use the comma).
see red trees ~ tread far, carefree daze
qwest fer rest, easy days
far few, fewer
crazed drawer fever
dratted sad wear
Now a real poet wouldn't feel constrained to tell you what her poem was about, but I can't help myself. I'm not a real poet. It's about how every fall I am compelled to clean closets and dressers after periods of doing nothing.
Go here to see how it's really done. This guy is a real poet.