Indices provide a concise way to write numbers in exponential form. The general rules of indices are: 1) Multiplication of indices keeps the base and adds the powers, 2) Division of indices keeps the base and subtracts the powers, 3) Raising a power to another power keeps the base and multiplies the powers. Indices allow large exponential numbers to be written more compactly using the relationship between the base number, index, and resulting value.