The flâneur was, first of all, a literary type from 19th century
The terms of flânerie date to the 16th or 17th century, denoting strolling, idling, often with the connotation of wasting time. But it was in the 19th century that a rich set of meanings and definitions surrounding the flâneur took shape. 
The flâneur was defined in a long article in Larousse’s
By then, the term had already developed a rich set of associations.
In the 1860s, in the midst of the rebuilding of Paris under
The crowd is his element, as the air is that of birds and water of fishes. His passion and his profession are to become one flesh with the crowd. For the perfect flâneur, for the passionate spectator, it is an immense joy to set up house in the heart of the multitude, amid the ebb and flow of movement, in the midst of the fugitive and the infinite. To be away from home and yet to feel oneself everywhere at home; to see the world, to be at the centre of the world, and yet to remain hidden from the world—impartial natures which the tongue can but clumsily define. The spectator is a prince who everywhere rejoices in his incognito. The lover of life makes the whole world his family, just like the lover of the fair sex who builds up his family from all the beautiful women that he has ever found, or that are or are not—to be found; or the lover of pictures who lives in a magical society of dreams painted on canvas. Thus the lover of universal life enters into the crowd as though it were an immense reservoir of electrical energy. Or we might liken him to a mirror as vast as the crowd itself; or to a kaleidoscope gifted with consciousness, responding to each one of its movements and reproducing the multiplicity of life and the flickering grace of all the elements of life.— Charles Baudelaire, "The Painter of Modern Life", (New York: Da Capo Press, 1964). Orig. published in Le Figaro, in 1863.
Drawing on Fournel, and on his analysis of the poetry of Baudelaire,
In these texts, the flâneur was often juxtaposed to the figure of the
In the decades since Benjamin, the flâneur has been the subject of a remarkable number of appropriations and interpretations. The figure of the flâneur has been used—among other things—to explain modern, urban experience, to explain urban spectatorship, to explain the class tensions and gender divisions of the nineteenth-century city, to describe modern alienation, to explain the sources of mass culture, to explain the postmodern spectatorial gaze.  And it has served as a source of inspiration to writers and artists.