Refinancing means taking out a new loan to pay off an existing one, usually to get a lower rate, a different term, or both.
It only helps if the saving survives the costs of doing it — arrangement fees, valuation, and any early-repayment penalty on the old loan. There is also a trap in resetting the term: moving to a lower rate but restarting a thirty-year clock can increase total interest even though the monthly payment falls. Compare total remaining cost, not the monthly figure.