A flush mount is a type of lighting fixture which fits tight to the ceiling without any gaps or hanging parts. They hold a single central bulb and have set screws to hold a globe in place around it. They originated in the 1940's-1950's when new styles of the post-war era housing had lower ceilings. These type of fixtures are mostly seen  in utilitarian rooms and bedrooms. Your choice of any glass shade or globe can give it a Victorian, Art Deco or Moderne flair.