There are three factors that determine the quality and feel of a sheet: The fiber from which it is made, how the fabric is woven and the thread count.
Fibre: Bed linen is available in different types of fibres such as cotton, Egyptian cotton, Supima, Silk, flannel/brushed cotton etc.
Thread count (TC) is a measure of the fineness of your fabric. It is measured by counting the number of threads contained in one square inch of fabric. A thread count higher than 180 is considered percale. A higher thread count does not necessarily mean superior sheets. A 400 thread count is about the limit that you can get onto a loom. If you’re seeing very high thread counts, keep in mind that manufacturers often achieve the high count by jamming in extra thinner pieces of yarn, which can double or even triple the count. Very high tread counts are heavier and can be so tightly woven, that the bed linen cannot breathe and you find that you perspire more, when using the sheets.
Weaving is the method of fabric production in which two distinct sets of yarns/threads are interlaced at right angles. The longitudinal threads are called the warp and the lateral threads are the weft or filling. The method in which these threads are inter-woven affects the characteristics of the fabric.
Two of the most popular choices for sheets are percale or sateen. A percale weave is a one-over, one-under structure. The threads are tightly woven, which results in a smooth texture and finish. Sateen sheets have a softer touch than percale sheets. The sheen and softer feel of sateen is produced through the satin weave structure. Warp yarns are floated over the weft yarns, for example four over and one under. The sheen of the fabric is because light is not scattered so much during the weaving process.