keep an eye on

VERB
14 LETTERS · STARTS WITH K

keep an eye on is a valid 14-letter word worth 20 points in Scrabble and 22 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
K5E1E1P3A1N1E1Y4E1O1N1
5 + 1 + 1 + 3 + 0 + 1 + 1 + 0 + 1 + 4 + 1 + 0 + 1 + 1 =20 PTS
DOUBLE WORD → 40TRIPLE WORD → 60
MEANING

What does keep an eye on mean?