It means that you can see something, it seems to you that you can take it, it is close to you but in fact you can't. For example you can see cherries on the tree but you can take it because you do not have a ladder to teaк them off .
October 25, 2017
That means that you can't get certain thing, though it seems that you can do it easily.
Literally "an eye sees, but a tooth does not reach"