what is the "#" do?

Question

im new to this and want to know how the # works. hope someone will answer my question thanks and more power.

Answer 1

In wich context?

It could be the prefix of hexadecimal code for colors in Html/Css...
Or the prefix for identify an id value in Css selectors (and in JS methods querySelector() and querySelectorAll, but not getElementById(), and in URL ( when appending a name prefixed with # to an URL, the page will be scrolled as much for having the corresponding element being displayed...