The LIBOR is among the most common of benchmark interest rate indexes used to make adjustments to adjustable rate mortgages.

The London Interbank Offered Rate (or LIBOR) is a daily reference rate based on the interest rates at which banks borrow unsecured funds from banks in the London wholesale money market (or interbank market). It is roughly comparable to the U.S. Federal funds rate. (Source: Wikipedia)

It is a standard financial index used in U.S. capital markets and can be found in the Wall Street Journal. In general, its changes have been smaller than changes in the prime rate. It's an index that is used to set the cost of various variable-rate loans. Lenders use such an index, which varies, to adjust interest rates as economic conditions change. They then add a certain number of percentage points called a margin, which doesn't vary, to the index to establish the interest rate you must pay. When this index goes up, interest rates on any loans tied to it also go up. Although it is increasingly used for consumer loans, it has traditionally been a reference figure for corporate financial transactions. (Source: BankRate)