Urban design is the design of towns and cities, streets and spaces. It is  the collaborative and multi-disciplinary process of shaping the physical setting for life in cities, towns and villages; the art of making places; design in an urban context. Urban design involves the design of buildings, groups of buildings, spaces and landscapes, and the establishment of frameworks and processes that facilitate successful development.

Source : http://www.udg.org.uk/about/what-is-urban-design