Please explain in detail the difference between one pole and two pole circuit breakers. Thank you.

1 pole.

That aside.

A two pole breaker breaks bots hots of say a 220 volt line whrereas a 1 pole breaker is usually reserved for 120 Volts.

You do have to be careful with breakers. One variety(tandem) put 2 ea 120 Volt independent breakers in a single space whereas a ganged breaker is used for 220 volt service. When one leg trips, the other does too. The first contains 2 single pole breakers and the second case, 1 two pole breaker.