“Stupid” questions thread

r/​Fitness does a weekly “Moronic Monday”, a judgment-free thread where people can ask questions that they would ordinarily feel embarrassed for not knowing the answer to. I thought this seemed like a useful thing to have here—after all, the concepts discussed on LessWrong are probably at least a little harder to grasp than those of weightlifting. Plus, I have a few stupid questions of my own, so it doesn’t seem unreasonable that other people might as well.