Refinancing occurs when you get a new mortgage to replace your old mortgage. This is done if your original rate was high then you could switch to a fixed rate with lower interest. To refinance, however, you should have excellent credit. If you have bad credit, or a lot of debt, refinancing might not be the best option for you.
Before you refinance, you should figure out how long you are planning to stay in your house. If you are planning on moving in a couple years, then it would not make sense to refinance because you would not break even on the closing costs in such a short amount of time.