Digital Video - Basics

A video file is made up of numerous technical elements. 

A video is composed of Pixels which are the smallest unit of a picture on screen. These square elements all combine to make a Frame.

A Frame is a single 'snapshot' of a video. Multiple frames played one after another in quick succession makes a movie. 

The Frame Size is the size of the frame which is measured by Pixel dimensions (height and width.)

The Resolution of a video refers to the number of pixels in the frame. 

The higher the resolution, the clearer the image will become. (4K resolution is sharper and more detailed with Standard Definition.)

The article goes into more detail about these concepts.