I'd suggest looking into Index Funds/ETFs if you're just starting out. They're relatively low risk (compared to just buying shares of stock in one company) and a great way to get a feel for how the stock market works. Index Funds and ETFs are basically funds that house stocks from many different companies. This gives you the ability to buy fractions of shares from multiple different companies instead of having to buy one share of stock from each company separately. This is a great way to spread out risk.
Let's say you decide to invest in VOO (Vanguard's ETF that tracks the S&P 500 - the 500 largest U.S. publicly traded companies). If Apple and Microsoft are both companies in that ETF and Apple, for whatever reason, goes out of business all of a sudden, you won't lose all the money you've invested. You have Microsoft and all the other 498 companies in that ETF that still hold value and prevent the whole fund from tanking. Now, if you had decided to only invest in Apple in the beginning, you would've lost most, if not all, of your money.
That's just a quick summary of one way to invest in the stock market. There's a lot of information out there for you to learn about and a ton of different options. I'd recommend checking out NerdWallet and Investopedia to learn more. They're great websites that have helped me over the years. Good luck! Investing and saving for the future is a very responsible (and fun!) thing to do.
Jessica recommends the following next steps:
As the above answers mentioned, you do have to be 18 unless you have your parents be joint-owners of the account. I recommend starting with a small deposit of money and get a feel for the stock market and how it works. The earlier the better. My favorite books that helped teach me are "The Warren Buffet Way" and "The Intelligent Investor". If you're not a book worm like myself, I recommend downloading yahoo finance app and subscribing to Morning Brew email newsletter.