let me help.. matte painting is a technique where you create an imaginary background by combining several different pictures together and make it appear seamless. It helps to reduce cost of developing a set for particular scene, but not necessarily so.
Matte painting used in many hollywood films such as Fast and Furious, Prince of Persia, X-men Wolverine and many more.
A matte painting is a painted representation of a landscape, set, or distant location that allows filmmakers to create the illusion of an environment that would otherwise be too expensive or impossible to build or visit. Historically, matte painters and film technicians have used various techniques to combine a matte-painted image with live-action footage. At its best, depending on the skill levels of the artists and technicians, the effect is "seamless" and creates environments that would otherwise be impossible to film.
Traditionally, matte paintings were made by artists using paints or pastels on large sheets of glass for integrating with the live-action footage.