In a weaving, the warp is the set of threads that runs vertically. It is held stationary while the other threads are interwoven with it.
Weaving is accomplished by lacing together two sets of threads. These threads are put at right angles to one another. There are vertical threads (the warp) and horizontal threads (the weft).
In traditional weaving, hand looms were used. These looms would typically hold the warp threads stationary on two frames. The weft thread would be on a device called a shuttle. The shuttle would be passed back and forth among the warp threads. The weft threads would go over and under alternate threads from the warp. This would result in the two sets of threads becoming interlaced into one piece of woven cloth.
In a weaving, the wrap is the thread that runs vertically in the cloth.