Good and well can both talk about positive quality, but they do not usually do the same job in a sentence. Good is usually an adjective, so it describes a noun or follows a linking verb. Well is usually an adverb, so it describes how an action happens.

Use good to describe a noun. Use good after linking verbs such as be, seem, look, and feel when it describes the person, thing, or situation. In these patterns, good means positive, acceptable, pleasant, or healthy, although after feel some speakers also say good where others expect well.

Use well as an adverb to describe how someone does an action. It often comes after the verb, or after the object. In these positions, well answers the question how.

Well can also be an adjective with the meaning healthy. After be, feel, seem, and look, English may use well when the meaning is about health. Good is also common in informal English, especially after feel, so this point has some variation in real use.

You can now choose between good and well in simple sentences. Choose good for nouns and after linking verbs when it describes the subject. Choose well for actions when it describes how someone does something, and use well for health when that meaning is clear.