New Urbanism is an urban design idea that encourages building walkable communities. The idea is that to be sustainable we must start with our way of life. Introducing green techniques and green building methods do their part in helping the environment but the real way to be sustainable is to live sustainable. By building walkable communities it encourages people to not own cars, live closer to the city, own smaller homes, etc. The hopes of many new urbanism designs are that people live in work in the same area.
Because new urbanism has a foundation of sustainability, most plans try to use the existing infrastructure and existing city structures in their design. Reuse is better than building new communities, but there are some new urbanists that take vacant areas and try to create a brand new neighborhood.
Suburban sprawl is the opposite of new urbanism. Suburban sprawl relies on the use of cars, houses are spread out, and people do not live and work close by. New urbanism tries to integrate commercial and residential into a single neighborhood making a mixed use community. For the most part everything should be within walking distance to a personal home in a perfectly designed new urbanism community.