Urban design describes a range of approaches to making towns better places to live. They can come from active citizens or from one of many professions: landscape architects, artists, ecologists, transport planners, architects, economists, surveyors and so forth. There are academic courses in urban design but there is no agreed curriculum and no control by a professional body. This is as it should be - because there are so many ways in which cities can be improved.
Wikipedia explains that 'Urban design is the process of designing and shaping cities, towns and villages. Whereas architecture focuses on individual buildings, urban design address the larger scale of groups of buildings, of streets and public spaces, whole neighborhoods and districts, and entire cities,basically the shaping of masses and spaces (solids & voids) to make urban areas functional, attractive, and sustainable.'
The landscape architects' contribution to urban design comes from their special skill in composing the five elements of landform, water, vegetation, buildings and pathways. The skill is learned a the scale of garden-size spaces and remains important at the scale of villages, towns, cities, city regions and tracts of landscape. The plans of many of the world's most admired cities are based on ideas developed in gardens - and landscape urbanism is a modern name for this approach.
'Urban' is an adjective and 'town' is a noun. So you can't design an 'urban' but you can design a 'town'. The English word urban comes from the Latin word urbÄnus meaning 'characteristic of, a town or city, esp. as opposed to the countryside' so 'urban design' can be read, not very usefully, as 'making a town more like a town'. So we need to remember that the cities were places where one could expect civilised behaviour - unlike the rough behaviour of the countryside.
The below examples, from China and Canada, are of Modernist Urbanisation. The design method was to lay out a grid-ish network of roads, fill the spaces with buildings and put a few plants around the buildings. This is not a Landscape Architecture Approach to urban design - which uses a different design method: (1) start by designing a public realm as a useful, beautiful and sustainable landscape (2) create the landscape space by arranging landform, water and planting in relation to buildings , routeways.
Urban design by architects and civil engineers. Note how the different dwelling types are carefully placed beside each other, like keeping one drawer for socks and one for pants.
Urban design by civil engineers and architects, with tastefully formal and informaal road patterns.
England, Essex, 1987. Urban design?
England, Seaburn, 1970. Urban landscape design?
France, Lille. Urban landscape design?
Poland, 1945. Urban landscape design?
Garden design, town design and landscape design. See Landscape & Urbanism