Pixels or pels (picture elements) in digital imaging are small little dots that make up the images. Pixel is the basic unit or smallest element a of programmable color in a digital image.
Pixels definition
Pixel is a single point of illumination on a digital display screen.
Collection of several pixels make up the images on digital display screens such as a computer monitor. A digital screen is divided up into a matrix of thousands or even millions of pixels. The quality of a display screen largely depends on the number of pixels on the entire screen called screen resolution.
In context of camera sensors, the term pixel is used to refer to a single scalar element of a multi-component representation (more precisely called a photosite in the camera sensor context).