Freelancing doesn’t mean that you need to work for free. But is the term used for the work done as freelancers. Freelancer is a self-employed and hired to work for different companies on particular assignments.

You need not to have a particular skill to get a work. The following are some of the categories.

Web, Mobile & Software Dev
IT & Networking
Data Science & Analytics
Engineering & Architecture
Design & Creative
Admin Support
Customer Service
Sales & Marketing
Accounting & Consulting

During Registration check Freelancers FAQ to see how will you receive payments. It is easy to receive payments.
It is global Leader in providing work to Freelancers. Creating Freelancers account is free here and have million of clients who are ready to offer Jobs and work.
Fiverr is a mini-freelancing website where you can simply showcase your skills and attract clients/customers towards your products and creativity. You can start making easy money with Fiverr which starts from $5 and eventually end up with thousands of dollars.
Specifically for web designers and web developers. Visit site to Creat Free account
If you are good in Writing then this place is all yours. Make Money with your writing Skills

If you are new to Feelancing the you do need to invest time in understanding it. But once you get your first job and some clients.

Best of Luck, In case of any question Please comment.