difference* ;) They all mean the same thing, just different ways of expressing it. However, there's subtle differences between them. To be good at something - Plain and simple, to perform something well To have an eye for something - I would use this when saying about something specific, for example...he has an eye for spotting mistakes when nobody else can. To know a thing or two about something - I would use this when trying to be humble and not brag about my skills. If somebody asks me if I am good at fixing computers, I can say, oh, I know a thing or two about it. :)