About Fabric Weave Types
Fabric is woven from "Weft" yarns, which run sideways across the loom, and therefore across the fabric; and "Warp" yarns, which run along the length of the fabric.
Types of Weaves
In weaving, yarns are interlaced according to preset patterns, or weaves. The yarn count and number of warp and weft yarns to the square inch determine the closeness or looseness of a weave. Woven fabrics may also be varied by the proportion of warp yarns to weft yarns. The most basic weaves are plain, satin, and twill.
The plain weave is the simplest of all weaves, a simple over and under, alternating each thread, to make a "checkerboard" pattern. It is also the strongest of the basic weaves because the yarns are tightly interlaced. The advantage of this weave is that the very light cloths can be achieved, so it is suitable for making the very lightest down proof fabric for duvets. However, it is quite plain in appearance.
The surface of satin weave cloth is almost made up entirely of warp or filling floats*, since in the repeat of the weave each yarn of the one system passes or floats over (or under) all but one yarn of the opposite yarn system. While the highest thread counts are made with this weave, the resulting fabric weighs a little more than what can be achieved with plain weaves. It is very pleasing to the eye, and may have a simple, smooth lustrous appearance, or have patterns woven into it. Sateen is a particular style of satin weave.
*Simply put, the float is the portion of the yarn that you see, which extends over two or more threads.
The difference between satin and sateen is the fact that sateen floats are made up of weft yarns, rather than of warp yarns.
Denim is the best known twill. It is identified by the quite visible diagonal lines in the fabric, and is often a simple "over two, under one" weave. Heavier fabrics are made this way, and they are suitable for featherproof applications such as feather pillows and featherbeds.
Thread Count & Weave Type are separate from each other
There are unfortunately many manufacturer's, marketers and retailers who say that a low thread count is a percale sheet and a high thread count is a sateen sheet. This is simply untrue. As you can see above, percale and sateen are merely weave patterns and have nothing to do with the actual thread count of the sheet.
It is likely this unfounded statement is due to the fact that most low thread count sheets are percale, merely a coincidence.