Shorting the two crystal pins and the blink program still works

Hi, I am doing an experiment with my Uno by shorting the two crystal pins. I thought the LED blinking program would stop, but the LED kept blinking. Does the Uno use its internal 8Mhz crystal if the external clock stops working? Will it work continuously? Since there are many kind of clone board, do all of them have internal crystal?

If I short the crystal pins and then connect the USB to the computer, the blink program works, but there is no connection to the computer.

You are probably shoring the crystal on the processor that does the USB to TTL conversion, not the mega328. On the R3 Uno, a 16MHz resonator is used instead of a crystal on the mega328.