What does apple of my eye mean?

apple of my eye meaning in Urban Dictionary

One's favorite individual; the main one you love most.In Old English, the student of the eye (the round, dark center) had been called the 'apple'. It was thought that the student had been a round object just like an apple (a bit of fruit). Once you have a look at someone, their reflection appears within student. So if someone is the 'apple of the eye', she or he is some one which you look at a great deal and luxuriate in seeing.