Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

What does it mean when someone says “FTSE closed at xxx today”
FTSE is an index catering to the London stock exchange. It is a  Capitalization-Weighted Index  of 100 companies listed on the London Stock Exchange with the highest market capitalization . When somebody says FTSE closed at 6440, it basically means at the end of the day, the index calculated using the day end market capitalization of the companies, included in the index, is 6440.