Pile rugs are rugs with (surprise!) a pile. Historians think pile rugs were developed to mimic the warmth of animal pelts. They are plush and cushy and soft. This softness is the result of thousands of knots wrapped around warp and weft strings and then cut (or, occasionally, left uncut). The longer the knot ends, the longer the pile, and the plusher the rug. One side of the rug (usually the back, except in some Berber rugs) will be flat, with all the knot ends on the opposite side creating the pile. If the pile is very long, the intended pattern may be partially masked — this is often intended by Moroccan weavers; over time, as the carpet is used the pile will wear down and the design will slowly, magically emerge.
Flat weave rugs are rugs that are not knotted and thus have no pile. Rather, the pattern is developed by using wefts of different colors. Wefts are interlaced with warp threads and changed out for whichever color is required. Flat weaves are often called kilims, hanbels, or plain weaves, although these are really specific subsets of the flat weave.
I love both Moroccan pile rugs and Moroccan flat weaves. Pile rugs feel incredible under bare feet and are the ultimate in cozy. I adore loose tribal patterning, whether in the beiges, blacks and browns of the Moroccan Beni Ouarain rugs or in rich vivid coloring of the Moroccan Boujad carpets. Nothing can compare to a pile rug. That said, I also have a real soft spot for Moroccan kilims. They are a fantastic way to add pattern in a room and are always the star attraction. I also am crazy about how forgiving they are – coffee or wine spills? Not a problem. Moroccan flat weaves always feel so fresh to me.