In this case "the conventions of the art world" refers more to technical concepts like perspective, composition, color theory, etc. In this way, outsider art is

In this case "the conventions of the art world" refers more to technical concepts like perspective, composition, color theory, etc. In this way, outsider art is distinguished from naive art. I personally think the distinction is flimsy, but humans do like to create these kinds of taxonomy. Folk art is another similar, but somehow technically different genre of art. It has less to do with the people in the art world: gallery owners, agents, critics, etc. Artists who meet the definition of outsider artists had their work shown in the traditional way, like Grandma Moses, Horace Pippin, etc.