There are hundreds if not thousands of ways to make money online. If you are under 18 years of age, that will restrict many of your possibilities as legal liabilities become an issue. I am not up on under 18 laws of employment and rules, but if you can have a parent open a paypal account for you, tie it to a bank account and that will open up your possibilities.
If you are 18 or older, the Internet is yours. Depending on your knowledge and talents, determines what you can do to make money online. Can you create websites or blogs? Graphic artist or photographer (sell pictures, images, logos...). An expert in any field? Several sites pay for answers - $20 per answer is not uncommon. Start a blog (almost any subject), gain a following and monetize it selling products or advertising. If your content is valuable and in demand, create a membership site.
Hard to advise you without more details but hopefully I have provided some ideas you can use.