A paracosm is an imaginary or constructed world. It's meaning, literally, is "beyond-world." Many people create these worlds as a hobby, a process often called worldbuilding. The most familiar use of a paracosm is for writers (particularly fantasy authors) who craft these worlds where their characters live and stories unfold. Paracosms can be simple sketches or fully-drawn worlds of astounding detail, with their own inventive histories, societies, and mythologies.