How did Brexit wipe $2 trillion off world markets? I read here (https://www.theguardian.com/business/live/2016/jun/24/global-markets-ftse-pound-uk-leave-eu-brexit-live-updates) and elsewhere that Brexit wiped \$2tr off world markets.

How did that happen?

Is this equivalent to \$2tr worth of a certain good, sinking to the bottom of the ocean?
Think about it this way:

You own 100 houses on a private island in Italy. These houses could be sold for $1 million each. 

All of a sudden, the Italian prime minister outlaws all boats. There is now no way to get onto the island apart from swimming.

Since you can no longer get onto the island by boat, and have to swim, no one wants to live in your houses, and thus no one wants to buy them for \$1 million. Your houses are still quite nice, though, so people instead will offer to buy them for $200,000. 

Your houses were originally worth \$100 million in total (that's how much you would have got if you sold them) but are now only worth $20 million. You have 'lost' \$80 million. 

In Brexit, instead of houses, we have stocks. These stocks were originally worth a certain amount of money. When Brexit occurred, people no longer wanted to buy or own British things, because they thought that they would be worth less. The total value of British things dropped by $2 trillion. It's important to note that the things are still there (the stocks didn't disappear!) but are simply valued less to investors.