HTML 4.0 & DHTML

To all,

Good day! I'm just wondering, why is there HTML 4.0 & why is there DHTML? Is
one a subset of the other? What are the components of DHTML not found in
HTML 4.0 and vise versa?

I conduct HTML 3.2 training. I have visited the W3C page and I learned that
HTML 4.0 talks more about CSS. If I upgrade to HTML 4.0, is HTML 5.0 or
higher just around the corner, waiting to be released?

Thanks in advance.

Dan