We know the market will crash now and then, but we also know it will keep going up after crashes. We don't take our money out of the market in fear. We have the guts to hold on to our stocks through crashes. These companies are usually very large and often very old. All the Dow's 30 stocks would be considered blue-chips.
Bonds are essentially loans that companies and governments sell in order to raise money.
If you buy a bond, you are lending money to whoever issued it, and you will usually collect some regular interest payments until your money is returned to you. Stockbrokers are agents who buy or sell stocks for the public. It's also kind of like a price tag for the whole company. If you wanted to buy the company, that's how much, at least, you'd have to cough up. To figure out a company's capitalization, you multiply the number of shares of the company that exist by the current price of a share.