What is Spec Work?
Spec work is any kind of creative work, either partial or completed, submitted by designers to prospective clients before designers secure both their work and equitable fees. Under these conditions, designers will often be asked to submit work in the guise of a contest or an entry exam on existing jobs as a “test” of their skill. In addition, designers normally lose all rights to their creative work because they failed to protect themselves with a contract or agreement. The clients often use this freely-gained work as they see fit without fear of legal repercussion.
A short video explaining why designers shouldn't work for free!
For more information take a look at https://www.nospec.com