Babel is notable for many reasons. It features stunning photography that took place in a number of different countries, a script that seamlessly weaves a number of different languages together into one narrative, from Arabic to English to Japanese sign language. It is also notable as an ensemble film, a film without a discernible "lead" character, but a number of different characters and storylines all of which have the same level of importance.
The "ensemble film" is as old as film itself, and dates back to 1916 with D.W. Griffith's epic silent film, Intolerance, which followed four parallel plots. Other recent ensemble films include Love, Actually; Pulp Fiction; Traffic; Magnolia; and Crash. While it is not required that ensemble films feature storylines with characters that do not know each other or overlap, this anonymity paired with interconnectivity is often a feature of the ensemble film.
Less narrowly defined, "ensemble films" are any films with a somewhat equitable distribution of significance given to different characters. In this definition, there is not a requirement that the characters be unconnected to one another. Robert Altman films such as Nashville, A Wedding, and Gosford Park typify this genre. The list of ensemble films is quite diverse, including but not limited to I'm Not There, Citizen Kane, Daughters of the Dust, The Breakfast Club, Dogville, Drop Dead Gorgeous, and The Godfather.