Sampling is used widely in computer graphics, especially in rendering (transforming a 3-Dimensional scene to a 2D image by simulating the way light would illuminate, reflect, reflect, etc. objects in the scene).
Samples are used in anti-aliasing, simulating cameras with depth of field, sampling lights to create soft shadows, and sampling BRDFS.
Several sampling methods are illustrated below. Click the image to get a description and animation of the technique.