The word "freelance" comes from the English language, which is used to refer to independent, autonomous or self-employed work. A freelancer is a person who works in freelance to provide services or products derived from their profession to third parties.
The freelancer's way of working is such that he does not have time-based contracts or contracts that oblige him to be affiliated to any company. It moves according to projects and contracts that are limited to them. But, the freelancer's main quality is that the worker makes the decisions relevant to his trade and assigns his own rules; so this could even be that he is hired for a matter of months to do something specific. It is this freedom that the freelancer has that many people seek when leaving their jobs, among other advantages (see more here). The important thing to distinguish between a traditional office job and freelancing is that the freelancer is paid as the freelancer chooses. The freelancer chooses whether it is per hour, per scope, or per project. In this way the freelancer has the decision in his hands and does what suits him best when it comes to work.
Nowadays it is a very common way of working due to the technological possibilities, but above all, because of how you can work from anywhere. This opens the mind of employees to have much more freedom in their lives and still be able to support themselves financially.