Eadweard Muybridge is an important figure in the evolution of the cinema because of his weird name, enormous beard, and his series of photographs showing a galloping horse in 1878; assembled, they can be considered the first motion picture. By 1887, he had produced forty-eight others. This was his second.
You can guess what it's about from its title. The naked man shown is Muybridge himself. Although, because of its original technique and (almost certainly) exhibition, it isn't a movie as we understand the term, it is a study of movement. Combined with equipment to record and display pictures over time, and using techniques derived from an understanding of persistence of vision, it remains a key step in the rise of this still-young (because of the antiquity of others) art.
Also because the subject suggests the first 'true' motion picture, Edison's BLACKSMITH SCENE.