What does it mean when someone says “FTSE closed at xxx today”
It's sort of the sum of stock prices, but bigger companies are weighed more heavily.
Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
What does it mean when someone says “FTSE closed at xxx today”

### Response:
It's sort of the sum of stock prices, but bigger companies are weighed more heavily.