i didnt understnd the basic concept of kriya visheshan

they tell us the visheshtaiyen of the kriyas.
Eg. mohan accha hai. in here accha is visheshan because it is telling visheshta of the sangya mohan.
     mohan accha gata hai. in here accha has now become kriyavisheshan because it is telling visheshta of the kriya gaana. it is telling how mohan sings.