How do you tell if a tire is tube or tubeless?

A tubular tire is a tire where the air bladder, the more durable outer rubber and the cloth layer(s) giving it all strength is assembled (and treated by the rider) as one unit. It needs a special rim where it's glued in place on to a shallow concave surface. To the extent they're still used they're almost exclusively used for road bikes, although TUFO have a MTB version as well. Tubeless today usually means the so called UST tires. They're used together with special valves, rim tapes and liquid sealants to get a wheel very similar to car wheels in construction. But don't forget the old,( a.k.a. clincher tire) that's used together with a separate inner tube. The tire cross section is like the letter U, and it's used together with a rim that's also like an U. Rim lips are pointing out and overlapping the tire lips that are pointing in.