Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

How do I invest and buy/sell stocks?  What does “use a broker” mean?
Very simple. You open an account with a broker who will do the trades for you. Then you give the broker orders to buy and sell (and the money to pay for the purchases). That's it. In the old days, you would call on the phone (remember, in all the movies, "Sell, sell!!!!"? That's how), now every decent broker has an online trading platform. If you don't want to have "additional value" and just trade - there are many online discount brokers (ETrade, ScotTrade, TD Ameritrade, and others) who offer pretty cheap trades and provide decent services and access to information. For more fees, you can also get advices and professional management where an investment manager will make the decisions for you (if you have several millions to invest, that is). After you open an account and login, you'll find a big green (usually) button which says "BUY". Stocks are traded on exchanges. For example the NYSE and the NASDAQ are the most common US exchanges (there's another one called "pink sheets", but its a different kind of animal), there are also stock exchanges in Europe (notably London, Frankfurt, Paris, Moscow) and Asia (notably Hong Kong, Shanghai, Tokyo). Many trading platforms (ETrade, that I use, for example) allow investing on some of those as well.