What are the warp strings and the weft thread?

Warp strings are the vertical strings which serve as the foundation of the rug. Cotton warp strings may not tolerate rough use as a floor covering. Weft threads are the horizontal strands of wool yarn that are woven in and out of the warp strings. As the warp strings are moved back and forth they disappear under the weft threads. If warp strings are showing on a finished rug something went wrong in the weaving.