The definitions below are layman definitions
Pixel - Contraction of the words picture and element. The smallest item of information in a picture. It's essentially a colored dot. A series of dots would form a line, clumps of it will form a picture of parts of it. The number of pixels arranged horizontally and vertically is equivalent to the resolution.
Resolution
Common terminologies in video security
CIF - 352 X 288 pixels (Regula TV resolution)
VGA - 640 X 480 pixels
D1 - 720 X 480 (DVD quality resolution)
Frame rate