The main difference between good and well is:
Good is an adjective and well is an adverb.
Sarah paints well.
Jim is a good painter.
Things become confusing after linking verbs; we use good after linking verbs such as: be, taste, sound, smell, look, seem and feel if we want to describe the subject, not the action of the verb:
The film wasn’t good at all.
This dish smells good to me.
I feel good today.
We use well after the linking verbs: be, feel, look and seem if we want to use the adjective form of well meaning ’healthy’:
Jim feels well enough to leave the hospital.
Fiona was well yesterday, but she feels sick today.