This circuit is a 555 IC operating in Astable mode with the rate set by the potentiometer and/or the capacitor at pins 6 and 2.
The 10k resistor is to protect the potentiometer from extreme current if the potentiometer is set to zero.
There are numerous circuits that can do this but this is just ONE of many using the 555 chip.
A metronome is a device that produces a steady audible click or other sound at a regular interval that can be set by the user to help musicians play or practice playing to a regular pulse. The pulse is measured in BPM (beats-per-minute). A tempo marking of 60 BPM equals one beat per second, while 120 BPM equals two beats per second.
