Introduction  Here’s what most people get wrong: a flannel shirt isn’t a plaid shirt. A flannel shirt is any shirt made from flannel, a soft woven fabric that’s brushed to feel warm and fuzzy. Plaid is just a pattern that shows up on a lot of them. The two get used like they mean the same thing, but they don’t.  Once that clicks, flannel makes more sense. It’s warm without being heavy, comfy from the first wear, and goes …