Digitally assembling multiple images into a final image. It also includes scaling, retouching and color correction of images. There is a wide range of software available in the market that enable us to composite.
One of the most common software readily available for compositing and other effects is Adobe After Effects.
Here is a vedio showing basic compositing using After Effects :
A video showing the 2D compositing on After Effects :
How can green screened footage be composited digitally?
Software now also allows for color correction, allowing digital images to have the authentic film look.
A fun video showing the myriad possibilities of composing digitally :