Percale:Percale is one of the most commonly used weaves for sheets. Also sometimes known as a plain weave, percale is a one yarn over, one yarn under weave. That means the warp (lengthwise threads) and weft (horizontal threads) will be equal in number. 

Flannel is generally made with either a twill or percale weave. The fabric is then napped to hide the weave. Napping is a finishing technique that gives flannel that signature fluffy, fuzzy feel. Flannel can be napped on just one side, or it can be double-napped, meaning both sides of the fabric are napped, for extra softness. Flannel is also often sheared after napping for a smoother texture.

 Flannel sheets, on the other hand, are great for keeping warm during the colder months. Flannel sheets are made of cotton or wool and are known for their softness and insulation.  When choosing flannel sheets, pay attention to the weight of the fabric, as heavier weights are generally warmer and more durable.  Choose flannel sheets that weigh 5 ounces or more for a comfortable and long-lasting option.