When someone asks ‘How are you?‘, what is the correct answer? ‘I’m good? /I’m well?‘ I have found an interesting article that explains why both answers are correct. You can read it here.
As it is explained in the article, as a general rule, ‘Well’ is an adverb and should modify a verb. Example: She did very well in the exam.
‘Good’ is an adjective and should modify a noun, a noun phrase or a pronoun. Example: She is a good student.