What's the difference between Play-Doh, modeling clay, and air-dry clay?

Play-Doh is a soft, reusable salt-and-flour compound that dries out if left uncovered, ideal for young kids and pretend play. Traditional modeling clay (plasticine-style) is oil-based and never dries, so it stays workable indefinitely but creations can't be kept hard. Air-dry clay cures in 24–48 hours without a kiln or oven, which is what older kids want when they're making keepsakes.