Spanish has two forms of the English "is". These two forms are "Estar" and "Ser". Ser is used for essential characteristics of a noun. Estar is used for conditions of a noun. Let me give an example. If I use the estar form and say "La manzana está verde", meaning "The apple is green", I would be suggesting that the apple is not yet ripe, since green is the condition of the apple. However, if I say the same sentence using the ser form, "La manzana es verde," I am saying that the apple is of a variety of apples that are green, such as Granny Smith apples.
In short, ser (soy, eres, es, somos, soís, son) describes "What" a noun is, and estar (estoy, estás, está, estamos, estaís, estan) describes "How" a noun is. Hope this helped.
The difference is between British and American English. As far as I know, "I'm good" is totally acceptable in AE (also as a response when someone asks if you want more water, for example - "No thanks, I'm good."). Takes some getting used to as a Brit, but after all, there is an American flag in the course icon ;-)
I agree with your understanding of the Spanish grammar, but I think your understanding of the English might be slightly misinformed. There has been the misconception floating around that, in response to the question "How are you?" after a greeting, "I am well" is more grammatically correct than "I am good". (I already wrote a comment about this misconception above, but I'll put another concise one here.)
Firstly, in this context, both "well" and "good" are functioning as adjectives (Nobody is "hungrily" when they want food or "tiredly" when they could use a nap). Thus, the idea of "'well' is correct because it's an adverb" is off the table.
It follows, then, that the difference is in the meanings of the adjectives. In fact, saying one is "good" can refer to one being a "morally good" person; however, that isn't the only definition. On the other hand, "well" as an adjective means having recovered from an illness.
TL;DR: "Hi! How are you, my friend?" "I am good!" "How are you doing today after having been sick?" "I am well, that cold was nasty though."
I agree that "I am a good person" would be one understanding of that; however, is it truly the only understanding of "I am good"?
"I am well", on the other hand, refers to wellness—health, in other words.
(Personally, I usually wind up compromising by saying "I am doing well" in conversations)
It is the only correct understanding of the sentence.
I just spent about a half hour typing out a thorough explanation, then turned to swat at a fly and lost it all.
Suffice it to say, no matter how many people may say "I'm good," and intend it to mean they are well, or taken care of, or set, or whatever... it is incorrect to use that way. Good can be a noun or an adjective, but it is only correctly used as an adverb when the verb is a state-of-being verb.
" I see good," is only correct if 'good' is a noun. "My vision is good" is correct because 'good' is an adjective describing 'vision'. Otherwise, 'I see well" is correct.
"I smell good" is correct because your odor is apparently a state of being. "I smell well" denotes an interesting talent.
Why 'am' is not a state of being verb is beyond the scope of my expertise.
Sorry about the fly! I know firsthand how frustrating it is to write something out only to lose it.
I don't know whether your statement that I understood to mean "One uses adverbs, not adjectives, with linking verbs [state-of-being verbs]" is correct. (I'm referencing where you said "['good'] is only correctly used as an adverb when the verb is a state-of-being verb").
I also understand the verb "be" to be a linking verb (a state-of-being verb, as you called it). One is not "thirstily" when one would like a drink, nor "sleepily" when one would like to take a nap. In fact, when one "is well", the word "well" is an adjective, even though in most other usages it is an adverb, such as in the examples you mentioned. Also, if linking verbs required adverbs, wouldn't "I am well" also have to take on the role of meaning "I am a good person" since "well" is the adverb version of "good"?
This article by a Harvard grad SAT/ACT perfect-scorer who now works as a tutor goes more in-depth about that and gives the following examples:
"I am well = incorrect unless specifically referencing an illness
I am good = correct
I am doing well = correct"
He also gives some examples with another linking verb "to feel":
I feel well = incorrect unless specifically referencing a prior illness
I feel good = correct
I am feeling well = incorrect unless specifically referencing an illness
I am feeling good = correct"
I've noticed some fellow Duolingists(?) commenting that English "I am good" is incorrect grammar, whereas "I am well" is instead the correct response to "How are you?".
Wiktionary seems to indicate that saying "I am well" is only grammatically correct when it refers to having recovered from an illness. It says that using it in casual conversation as a response to "How are you?" is hypercorrect
The reasons for this include both that "to be" is classified as a linking verb, and that "well" as an adjective has a different meaning than "good" as an adjective, according to this blog post by a Harvard grad and high ed prep tutor.
Both these sources would lead me to believe that "I am good" is not only acceptable, but is perhaps even more grammatically correct than "I am well".
However, I suppose at the end of the day, the important thing is making sure the other person understands what you mean.
...says Glinda to Dorothy, explaining the difference between herself and the wicked witch? https://grammar.yourdictionary.com/grammar-rules-and-tips/when-to-use-good-and-when-to-use-well.html
The article does not say that "I am well" is only correct in response to a question after a sickness, and that assertion is simply false. The question "How are you"" is a question about well-being, which might apply post-sickness, but applies generally. The article suggests that a response focused on health might be, "I feel well" or about one's emotional state, "I feel good." There is no mention at all of "I am good" which means something entirely different. To respond "I am well" is not "hypercorrect," just correct. Yes, I know that everyone says, "I am good," but DL should teach correct English.
I agree with you that Duolingo should teach correct English; that's why I am an advocate of "I am good". Perhaps I could have been clearer: my conclusion is not based on the mentioned article (moreso on this one), I merely read it and noticed it seemed to have correct information, which was what I was commenting on.
(Upon reflection, I wonder if that adjective definition is why the word "wellness" refers to health.)
In my own personal conversations, however, I usually just respond with "I am doing well", in the sense of "I am faring well".
1) So would a Spanish speaker never say "Yo soy bien"? Would they always say "Estoy bien"? 2) So would a Spanish speaker never say, "Yo soy bueno?" 3) Does the bueno refer to me (me, being the noun?) OR does the "bien" refer to the "am" state (soy/estoy) - and please, please keep your answer simple. :)
To answer your first and second question: To say you are well/good/fine as your current state of being you would always use estoy instead of soy. If you use "yo soy bueno" instead, the meaning changes to you are a good person generally or you are good at what you do, not to how you are feeling/doing now. For more info look up ser vs. estar.
There is a longer explanation in an above comment, but the confusion lies in that Spanish has two different verbs that translate in English as to be. "(yo) soy" comes from the verb ser, and "(yo) estoy" comes from the verb estar. To learn more about the differences between the two, see the above reply to the question by Duh_Way, or look up "ser vs. estar" in your search engine of choice. If you still have questions about it, feel free to send them my way here. Gracias