Design-Build is a construction project delivery system where, in contrast to traditional "design-bid-build" the design and construction aspects are contracted for with a single entity known as the design-builder or design-build contractor.
Over the years, most major building projects have taken the form of design-bid-build, meaning an engineering firm designs it, the project owner puts it out to construction firms for bid and selects a general contractor, and then that contractor constructs the project. Design-Build is when an engineering firm and construction firm collaborates up front to present a bid to the project owner to design and build the project in a single package. This saves time, as it eliminates a step in the project sequence, and in many cases, construction on some phases can begin before the entire design process is complete. It can also reduce animosity between the engineering firm and contractor.