Copyright is complete ownership of a set of rights to creative works. When you create a new artwork, as the originator, you have copyright to the material, and as such can determine what commercial or non-commercial uses are and are not allowed for that material.
Copyright can live on beyond a creator’s death & can be passed on to heirs or transfer hands through other legal processes including work-for-hire contracts or buyouts. Once copyright expires, creative works become part of the public domain, and as such can freely be used by the public for commercial & non-commercial purposes.
It is important to note that copyright law has changed and expanded every time the copyright for Mickey Mouse was about to expire. Mickey Mouse is particularly important for illustrators to remember. We don’t remember Ub Iwerks, the man who drew Mickey Mouse, we remember Walt Disney (& the Walt Disney Company) who own the copyright to Mickey Mouse.