Adverbs are used to describe verbs. Adjectives are used to describe nouns. "It looks good" is perfectly good, because 'good' modifies 'it', not 'looks'. In "It looks well", 'well' modifies 'looks', which means that 'it' is very skilled at looking at things, which is clearly not what you're trying to say. By the way, "well" can sometimes be an adjective, but only when describing people. So it is also perfectly correct to say "You look well" or "he looks well".

It's a common way of simply saying "OK", or "I agree" For example- Stacie: Let's get dinner tonight. Max: Okay...what time? Stacie: How about 6pm? Max: Ok. Sounds good.

Yes, I'd agree with Jmat. The word good is describing a noun, not a verb. In the following dialogue for example: Do you like my new hairstyle? Yes, it looks good. The word 'good' refers to the hairstyle. Or in Altini's dialogue above, the comment 'Sounds good' or 'It sounds good' is your opinion of the suggestion. Good describes the idea (it) not the word verb 'sounds'. You could say both of the following to a friend, but they would have different meanings: You look good : You look nice, smart, pretty, attractive You look well: You look healthy, relaxed, stress-free