Why do you need a quartz resonator?

Question

Arduino

I started learning arduino. Already figured out some things. I want to do something on atmega8. Why do we need quartz resonators, what frequency to choose, is it possible to do without it?

Answer 1

Needed for external clocking. On atmega8 you can choose 8 or 16MHz. And it is possible without it. Depends on the task.

Answer 2

I note that a quartz resonator is needed not just for clocking, but for clocking with a stable frequency of a certain value. This is important if the controller uses UART to communicate with, for example, a computer.