these short descriptions I've read don't seem to answer this question for me - how is this different from orgmode + org-babel + HTML/PDF export? See like reinventing the wheel for one language, or am I missing something?
Pollen is a Racket language, and gets parsed into an AST and evaluated. You can programmatically generate correct markup using all of Racket.
Org Babel is more about evaluating code snippets in a variety of languages. Even if you can evaluate to produce org markup that's processed it doesn't have the same level of structural integration.
I'm not sure about that combination of tooling, but I consider pollen to be useful as markdown + customization. Ofc its a full general-purpose language to work with, but I myself just wanted it to solve adding sidenotes, footnotes and simple references.
I also noted others using to handle blog publishing tasks like latest post pages and tags and such
I guess in total its a general html publishing framework, and at least partly notable for being built in a lisp, given htnl's usage of basically s-expressions
