Difference between cross-over cable and straight-through cable

I tried to connect two computers by UTP cable, it worked on both straight-through and cross-over. Why?

The answer is when your computer have built-in auto-crossover (a.k.a. auto-switching or auto-MDI/MDIX) port that lets a computer connect directly to another computer using a straight-through cable. A crossover cable is also used to connect two hubs (or switches) if both hubs (or switches) don't have uplink ports.

Straight-through cable is used to connect a computer to a hub or a switch. It can also be used to connect two hubs (or switches) if each hub (or switch) has an uplink (i.e. built-in crossover) port.