"Good" and "well" are often misused. "Good" is an adjective (and a noun in some cases); "well" is used as an adverb unless used as an adjective meaning "healthy". If we need a word to describe noun or pronoun we use "good". If we need a word to describe verb (or sometimes adjective or other adverb) we use "well". For example:
Kate is a good piano player. (correct)
Kate is a well piano player. (incorrect!)
Kate plays the piano well. (correct)
Kate plays the piano good. (incorrect!)
Brian speaks good English, but he doesn't speak Spanish very well. (correct)
Brian speaks well English, but he doesn't speak Spanish very good. (incorrect)
My brother did well on the English test. (correct)
My brother did good on the English test. (incorrect!)
Do you think I'm doing well at school? (correct)
Do you think I'm doing good at school? (incorrect!)
After linking verbs such as be, taste, sound, smell, look, seem, appear we use the adjective "good" as we are describing the subject of the sentence, not the action of the verb:
The concert last night wasn't very good.
If the food tastes good, children will eat it.
Your idea sounds good and if it works would be great.
It always smells good after the rain.
The house looks good outside.
After the linking verbs "be", "feel", "look" we can also use "well" as an adjective meaning "healthy":
I am well. / I feel well. / I'm feeling well. (refers to physical state, health)
I am good. / I feel good. / I'm feeling good. (refers rather to emotional than physical state)
Jane didn't look well last night. (well = refers to heath)
The new dress looks really good on you. (good = refers to appearance)
Note: In the USA (conversational English) you can hear a lot of people answer "I'm good." in response to "How are you?" and it is very popular among young generation.