To add to Tsumi : "I feel very well" "I don't feel very well" - well = healthy (adjective).

I would provide such examples of using this word. - in the beginning of the sentence: well, I have to go= Ok, I have to go. - using it as an adverb, deriving from the adjective good: You have a good voice.= You sing well. - "as well" meaning also I would like to go to the cinema. But I'm willing to stay home as well

Just to further confuse you, in London slang 'well' is used instead of very : "How was your day?" "well good" (very good) My parents hate it though! And sometimes we use good where we should be using well! Also with "how are you" "Im good". This is technically wrong (although everyone says it) and it should be "Im well"