What actually happened
Banks bundled up millions of risky mortgages, sold them as 'safe' investments, and bet enormous sums on them. When people couldn't pay those mortgages, the bets unravelled and giant banks ran out of money almost overnight.
Why it happened
For years, lenders handed out mortgages to people who couldn't realistically repay them, because everyone made money selling the loan on to someone else. Nobody was left holding the risk, until suddenly everybody was.
How it hit your wallet
Millions lost jobs, homes and savings. Then governments spent hundreds of billions of taxpayer money to stop the banks failing. The people who took the risks largely kept their bonuses; the public absorbed the loss.