As simply as I can:

Arbitrage, options trading, currency trading and many other semi-exotic-sounding trading behaviors involve "leverage". You may have heard the phrase "margin trading" which involves "leverage" which is market-speak for "trading with money you don't have." Should you ever choose to play with Forex, for example, you will quickly learn that you can't make any real money without playing with REAL money - a "standard lot" in forex is 100,000 (dollars, euros, yuan, whatever). A "mini lot" is 10,000. And if the renminbi drops .05% against the dollar over the course of an evening, if you have twenty lots of dollars that you trade for the equivalent in renminbi, you made ten thousand dollars! Congrats! Of course, you staked two million dollars. And it might go back .07% tomorrow in which case you lost five thousand dollars. And you're renting that money, by the way, it isn't yours. You have leveraged the cash to play Forex.

Enter George Soros.

"At their desks on the other side of the Atlantic, Druckenmiller and Soros saw the rate hikes as an act of desperation by a dying man. They were a signal that the end was nigh--and that it was time for one last push to sell the life out of the British currency."