Ok. The 1st thing you need to decide is how you want to build your portfolio. If you're single with no kids and you like to take risks, for possible big returns, invest in small cap stocks. If you're trying to make money grow, invest in large-cap, to mid-cap stocks.
Also trading and investing are two different things. Investing is with the intention of hanging on for years, where trading can range from a day (day trading) to a few weeks. (Swing trading.)
I'm going to assume you're starting out. You should start out with Mutual Funds and/or EFT's (Exchange Traded Funds). Also understand that if you're not familiar with the game, you'll be paying a financial adviser for instruction and doing your trades which can affect your return. If you have an understanding of the game and want to trade/invest infrequently, you can holla at a discount broker. (i.e. Charles Schwab) You'll be doing you're research, as you should be regardless, but the rates will be lower.
There is also Commodities, bonds, options, futures, and currency trading. Avoid derivatives.
As a matter of fact, as Pico mentioned. get the for dummies books. You can find them on the net in PDF for free. Look for:
Stock Investing For Dummies
Mutual Funds For Dummies
Trading For Dummies
Day Trading For Dummies
EFT's for dummies