Did you know that the word freelance comes from a knight or mercenary who would sell his services to any lord willing to pay- hence he was a "free lance?"
In this same way, a freelance writer is a writer who works for a company or individual on a contractual , or project basis. These "contractual" positions don't even necessarily need to have a formal contract in place (although that's probably in your best interest as a writer) , but what they do have in common is that they are a project or piece of writing with a set time frame and a clear goal. After the project is complete, the free lance moves on to the next project
Somebody who is not specifically permanently employed as a writer, but writes anyway as a "self-employed" person. Their work is then ( hopefully ) seen to be good enough to be purchased by suitable clients.
Some freelance writers simply chase news-worthy stories and attempt to sell their reports to newspapers.
Some write screenplays for films and/or tv shows. Some write scripts for radio programmes.
Some write academic or similar "scholarly works" and have them published e.g. as distance learning material, particularly for courses covering units in newly published or amended syllabi.
A freelance writer is a writer who works for a company or individual on a contractual, or project basis.
There are many different kinds of freelance writing, such as business writing, marketing writing or web writing. On the other hand, some freelancers focus solely on querying and writing for magazines, anthologies or newspapers, while still others serve non-profits through grantwriting and proposal development.
You can find a lot of good freelance writer on freelancers site, but you need to check to see if hiring from them is reliable.