You asked a very simple but good question..
There are 100+ websites where you can make money online but all depends on the nature and volume of work.
You can become freelancer and work your way on Fiverr, upwork, guru, freelancer, 99designs, peopleperhour, textbroker and workchest websites.. and offer your service in return for money..
You can also do small tasks on micrworkers, picoworkers and amazon turk etc.
You can sell your photos and videos on istock, adobe, and shutterstock website.
You can sell your video courses on udemy, skillshare, coursera and make money online..
You can teach online on cambly, studypool and tutor.com etc. and make money.
You can launch your own blog and YouTube channel and make money through google adsense and youtube partner program.