[slap_shot]

simplified:

Exchanges are a group of public companies. Each company has a market capitalization, calculated by the number of shares * the share price.

Apple's individual market cap is greater than the aggregate market cap (sum of all companies' market caps in the exchange) in many other exchanges in the world.

It means what we already know: Apple is a very large company (it's the largest public company in the world).

[_hypx]

It is also unfortunately a sign of a market imbalance. There have been periods in history where one company or group of related companies held a ridiculously large percentage of stock market capitalization. They rarely last for long, and in the long run they always regress to the mean.