Canvas question

Good day
i’ve been trying to search the internet for the answer but no luck so far.
I want to know, i want to develop a website i know some basics of html5/css (just below average) but will learn more as i go along however as my second stage for the project I would like to implement drawing effects on couple of the website sections with Canvas.

My question
Can canvas be implemented into already exsiting code ?
Or does a website gets build on canvas right from the start?

Canvas can be built into existing code.

It simply hooks onto an html element through its id. You can see an example here.