what's the difference between bien and bon?

In one sentence: "bon/bonne/bons/bonnes" (=good) is the adjective, whereas "bien" (=well) is the adverb.
I know that this won't help much but it's a start.

You may want to check out this webpage:
https://www.thoughtco.com/bon-vs-bien-1368817

Greetings,
-- Chris.

Bonjour Dominic !

You might want to have a look at our lesson on mieux vs meilleur, which explains the difference of usage between bien and bon:

https://progress.lawlessfrench.com/revision/grammar/meilleur-mieux-pire-plus-mauvais-plus-mal-better-best-worse-and-worst-irregular-comparative-and-superlative-forms

Bonne journée !