From the book The Source of Living Water (Ki Tetze, Chapter 21): Man is called by four names according to his deeds: Adam, Ish, Gever, and Enosh.
Enosh (אנוש) points to the lowest, smallest level. This kind of person spends his whole life pursuing bodily passions and forgets about the source of his soul, where it is from, and where it will return in the end. He is called “Enosh” according to the verse, “God has made me forget (Nashani)….” (Beresheet, 41:51) because he forgot about his end.
Gever is a person who slightly overcomes (Mitgaber) and does not follow his lust like a beast, but is satisfied by what he finds. However, he does not limit himself out of the fear of the Creator, but because he understands that man has to be higher than a beast and not follow the urges of the bodily desires. He is called “Gever” because he slightly overcomes the evil lust. However, this is insufficient for the Light to clothe upon him because he does not aspire to the Creator, “When will I see the Creator’s face in order to give Him pleasure?”
Ish is the next level of development. It contains a hint at unity with the Creator through the qualities by which the world was created. This points to the good that is hidden inside a person, the reason why his soul desires the Creator’s teaching and the observance of His covenant in order to merge with the Light of life and give Him pleasure. But he is still motivated by egoism, which throws him off the path toward the Creator.
Adam is the highest level, originating from the words “I will become similar to the upper one” (Edameh le Elion) (Book of Joshua 14:14). This person has already come completely out of the three lower categories, in which he is similar to an animal, and he merges with the Creator. He unites his plans, words, deeds, and movements, concealed and revealed, in unity with the Creator, truly and sincerely, without any unrelated thoughts.