Specifically refers to someone who attends an exhibition, art show, or similar public display. More formal than 見物客.
The number of visitors to the art exhibition is increasing year by year.
Many of the visitors were earnestly appreciating the works.
Compound of 来 (come), 観 (view), and 者 (person). The exact historical derivation is uncertain, but the word follows a common Sino-Japanese pattern for designating a person who comes to view something.