As a freelancer you are self-employed and therefore you have a company, a sole proprietorship to be precise. The word says it all, I am alone!
Companies can hire me to do work, both for small jobs and for long-term collaborations. Sometimes an organization already has a marketing department, but they do not have the right knowledge and I assist with that. Sometimes it is also the case that a company is just starting up and has no active employees yet, everything is possible. A freelancer is only paid on the basis of the hours that he / she reports.