coordinate system

NOUN /koʊ'ɔrdənɪt_'sɪstəm/
17 LETTERS · STARTS WITH C

coordinate system is a valid 17-letter word worth 24 points in Scrabble and 26 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
C3O1O1R1D2I1N1A1T1E1S1Y4S1T1E1M3
3 + 1 + 1 + 1 + 2 + 1 + 1 + 1 + 1 + 1 + 0 + 1 + 4 + 1 + 1 + 1 + 3 =24 PTS
DOUBLE WORD → 48TRIPLE WORD → 72
MEANING

What does coordinate system mean?