A flannel shirt fabric is a particularly soft woven fabric that has undergone a special brushing treatment to get a fuzzy texture. Some flannels are brushed on only one side, while others are brushed on both sides. Many might be familiar with wool suiting flannels, but the majority of shirting flannels tend to be made with cotton.
Flannel fabrics are popular for casual wear in the colder months. Flannels will come in a variety of patterns, but most commonly either solids or plaids.