What is the difference between 1 pole and 2 pole circuit breaker

A 1-pole breaker (in the U.S.) is used with a typical 120v circuit, having one hot wire and one neutral wire.

A 2-pole circuit breaker is used with 220v circuits where current flows between two main wires and a neutral is not typically used. This is used for ranges, clothes dryers, etc. Both mains are switched.

A good first order definition. But there are two pole breakers such as 15/15, 15/20 and 20/20 Amp where the handles are not tied together. They typically fit in one space and supply two independent 120V circuits.

The maximum number of poles is not to be exceeded in a panel.

A good first order definition. But there are two pole breakers such as 15/15, 15/20 and 20/20 Amp where the handles are not tied together. They typically fit in one space and supply two independent 120V circuits.KISS, this is not considered a "two-pole" breaker. It is simply two single pole breakers in one space. A two pole breaker is just that, two poles switched together.

A two-pole breaker is not just for "220" circuits. More accurately it is for 240v, or 120/240v circuits.

A 120/240v circuit is something like a dryer or range. These circuits require a neutral since there are 240v and 120v loads within the appliance.

A multi-wire circuit (shared neutral) is something that can also have a two pole breaker. This is two 120v circuits shareing a neutral. The 2008 NEC has a change requiring a tied breaker for these circuits. A two-pole breaker is the easiest way of satisfying this requirement.

A straight 240v circuit is one that does not require a neutral. An example of this would be electric heat or an electric water heater.

I was going to correct that: The two single pole breakers in one housing concept. Didn't get a round to it.