Simply put, when you refinance a home mortgage loan, you pay off an existing home mortgage loan in exchange for a new home mortgage loan. The answers to "how", "when", "where", "who you choose to refinance with" etc. will all influence your decision to refinance your home mortgage loan.
Since your home is probably your most valuable asset, it is prudent to be well informed before you choose to work with any lender. Working with a qualified mortgage specialist, will help you understand all the pros and cons of your individual situation before you make that final decision.