Refinance can work in many ways.

The basic idea is as follows: you're not too keen on your current loan for whatever reason (payments, terms, whatever), so you go to a bank/broker and get a new loan paying off your old one. If your new loan is a 30 year loan, then your loan term will extend 30 years out from the refinance... the original loan is dead and gone at this point.

Another way people refinance is to borrow against the equity you have in the house... i.e. getting another loan in addition to the one you've already got. So you continue paying your old loan and you pay your new one too. People sometimes do this to pay for large projects, education or other big ticket items... most people do so foolishly.

You can do it for extra cash, you can do it for your current loan balance (no cash to you), or you can roll more of your personal cash into the loan to reduce your principal. Many ways to do it... pretty much any type of loan available for buying a house is also available for refinancing, so the options are near limitless.

If you're thinking about refinancing, be sure you've got a good grip on the consequences... a lot of people use their homes as a cash machine and end up in way over their heads.