A canvas is a rectangular area on an HTML page, and it is specified with the tag.
The HTML5 canvas element is used to draw graphics, on the fly, via scripting (usually JavaScript).
The canvas element is only a container for graphics.
To draw a graphic, one would need a script (usually JavaScript).
A canvas is simply a blank drawing area that can be used to draw any graphic (lines, rectangles, etc) or to put any available image.
It has no content by default. One HTML page may have more than 1 canvas inside.