I was directed to the following interesting article on ‘Invaluable site’, by Emma Welsh, from Community Outreach…

Outsider art refers to works created by self-taught, unconventional, and oftentimes, under-recognized artists. Until the 1980s, the term was synonymous with art brut, a French movement that translates to “raw art.” Art brut referred to any work produced by untrained artists made outside the academic tradition of fine art.

Though considered culturally marginal figures due to varying circumstances, outsider artists have been known to produce a diverse range of high-quality works. They share little to no assumptions or aesthetic styles, It is their process, rather, that unites them: creating without rules or fear of taboos. Thus, outsider art can be raw, extreme, and unconventional.