An index is an indicator or measure of something, and in finance, it typically refers to a statistical measure of the change in a securities market. In the case of financial markets, stock, and bond market indices consist of a hypothetical portfolio of securities representing a particular market or a segment of it. An index or power is a mathematical representation that indicates the number of times that a number is multiplied by itself. If a number is multiplied by itself m times, then it can be written as: a x a x a x a x a…m times = am. Here, a is called the base, and m is called the exponent or power or index. Indices are a useful way of more merely expressing large numbers. They also present us with many useful properties for manipulating them, using what is called the Law of Indies. Indices are a crucial part of the global investment business, used to benchmark and at the core of the investment decision-making process via index-tracking unit trusts and ETFs. Any fan of passive investing has to be aware of their choice, and use of a particular index is anything but a neutral decision.