Interpolation

Interpolation is the process of inserting new pixels between existing pixels.  The result is greater picture, and consequently, larger file. Interpolation was invented for enlarging of images for printing and other purposes. The interpolation was also used as good manipulation method for confuse the purchaser by  representing machine as better resolution source as really is.
Interpolation works on creating estimated values between existing pixels. Few methods are used for interpolating algorithm: linear, bilinear, bicubic and fractal. As best is the bicubic method considered. Still, some artifacts could be created, as ghosting, jaggies along diagonals, and noise that can become emphasized.
Interpolation, still, can't create details that are not captured with camera. It works better when used on larger pictures in small doses. By interpolating small files to a very large size, the picture can be degradated more as is detailed. In other side, when picture is interpolated to a smaller size, the noise and some other artifacts are reduced. Also, the sharpening process has stronger affect to smaller images.