Refinancing is when an original loan is paid off by a new loan on different terms. This is being considered by many people at the time of writing due to unusually low interest rates due to current economic conditions, but is more usually considered in order to obtain cash flow or change the terms of repayment. For example, the new loan could be over a longer period than the original one which would reduce the amount of each monthly repayment. Another example is where refinancing is done to obtain a new loan at a lower interest rate.
Although theoretically refinancing can be applied to any type of loan, it is usually applied to a mortgage. A mortgage is a loan taken out with real estate used as a security against failure to make repayments. The word "mortgage" comes from the French word "mort" meaning death, because prior to its invention, most loans required repayments from living things, either crops or livestock, so a mortgage was a loan with the security being a non-living thing.
Almost all original mortgages are loans taken out to pay for the same piece of real estate which is used as the security, but refinancing is sometimes used to obtain cash flow for other reasons, including personal or businesses financing of various types. Sometimes refinancing of a home is used to pay off other loans which are at a higher rate of interest, such as credit cards. Additionally, in some areas there might sometimes be particular tax advantages to refinancing.
Refinancing mortgage rates vary, so check current rates, but be careful to consider other factors such as opening and closing fees and penalties for early payment of the original loan