Flannel is usually made with brushed cotton or wool. It's thicker than other common weaves like sateen, percale, silk, or linen, so it feels insulating and cozy. It's brushed on one or both sides, which raises the fibers for a soft, fuzzy feel.

Brushing cotton when making flannel causes broken or loose threads, so it's prone to shedding. The shedding fibers cause lint.

Plaid refers to a checked pattern, whereas flannel is a specific type of fabric. Plenty of flannel sheets feature plaid patterns, which is why they frequently get confused.