Ftse 100 Index
In short
The FTSE 100 is a stock market index that tracks the performance of the 100 largest companies listed on the London Stock Exchange.
In plain words
It acts like a thermometer for the UK's biggest businesses. When the index goes up, it means the share prices of these top companies are generally rising. It is often called the 'Footsie'.
A simple example
If most of the big companies like Shell or HSBC see their share prices increase today, the FTSE 100 index value will rise.
Why it matters
It helps investors understand how the UK economy and large global corporations are performing. Many pension funds and savings plans use it as a benchmark for success.
Easy to mix up
Do not confuse it with the FTSE 250, which tracks medium-sized companies rather than the largest ones.