When you buy a stock, you own a little bit of a big company. If the company makes money, your stock might go up in value. If you company loses money, the stock may go down. They may also pay you a dividend.
To invest in stocks you will need a brokerage account at one of the online investment companies such as Fidelity, T. Rowe Price., AmeriTrade, or you visit a local stock broker and open an account. They will charge you money every time you buy and sell. Once you get money in your brokerage account you can begin selecting stocks to buy. Then watch them go up and down in value. Stocks can make big price moves in only a few days or hours, so keep an eye on things and manage your buys and sells and holds.
The good thing about owning individual stocks is the potential for big upward price moves. Of course there is also the potential for big downward price moves. Also, there is no tax liability until you sell the stock. You will have to research the stocks you wish to buy and manage your account. This takes knowledge, experience and wisdom.