What part does gravity play in the function of the water clock?

Question

.I kind of don't understand this question. All I need is a better understanding

Answer 1

Water flows down because of gravity.

Answer 2

Than you soooooooooooo much. You are a life saver. Thank you.

Answer 3

You are welcome of course. Google water clock by the way.

Answer 4

I do get the but could maybe explain me the question In easy version (if so)