A Freelancer is working for your self; this is a plain and simple explanation. He/she is not maintaining office schedule (ie.9 am to 5 pm). he/she has no boss. He /she work his own time. He/she works from home.
wikipedia: A freelancer, freelance worker, or freelance is a person who is self-employed and is not committed to a particular employer long-term. These workers are sometimes represented by a company or an agency that resells their labor and that of others to its clients with or without project management and labor contributed by its regular employees. Others are completely independent. "Independent contractor" would be the term used in a higher register of English.
Fields in which freelancing is common include: music, journalism, publishing, screenwriting, filmmaking, acting, photojournalism, cosmetics, fragrances, editing, photography, event planning, event management, copy editing, proofreading, indexing, copywriting, web design, computer programming, graphic design, website development, consulting, tour guiding, video editing, video production , translating, illustrating and micro jobs.
Freelancing is one the easiest, fastest and lowest cost way to start working for yourself. Multiple freelancing websites like, Odesk, Elance, Freelancer and 99design provide an online marketplace where employers post work and freelancers bid on completing the work in an open market, which is extremely competitive