" At its simplest, weaving involves two sets of threads: weft threads and warp threads. The warp threads are held tightly by a device called a loom. The process of weaving involves passing a weft thread over and under successive warp threads. This is the basic procedure to weave most kinds of cloth. In tapestry weaving, the warps are spaced widely enough that the weft slides down over them and completely hides the warp. Because the warp is hidden and the image we see is created by the weft alone, the weaving is called weft-faced. "

― Rebecca Mezoff , The Art of Tapestry Weaving: A Complete Guide to Mastering the Techniques for Making Images with Yarn