Though it is called a stock market or equity market and is primarily known for trading stocks/equities, other financial securities - like exchange traded funds (ETF), corporate bonds and derivatives based on stocks, commodities, currencies, and bonds - are also traded in the stock markets. (For related reading, see "What's the Difference Between the Equity Market and the Stock Market?")
When you buy a stock, you should have a good reason for doing so and an expectation of what the price will do if the reason is valid. At the same time, you should establish the point at which you will liquidate your holdings, especially if your reason is proven invalid or if the stock doesn’t react as expected when your expectation has been met. In other words, have an exit strategy before you buy the security and execute that strategy unemotionally.
You can profit from owning stocks by an increase in prices or quarterly dividend payments. Due to compound interest—which allows your interest to begin earning interest—investments accumulate over time and can yield a solid return. For example, if you make an initial $1,000 investment and add $100 monthly for 20 years, you'd end up with $74,457.50, even though you only contributed $25,000.