expanding upon

NOUN
14 LETTERS · STARTS WITH E

expanding upon is a valid 14-letter word worth 26 points in Scrabble and 33 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
E1X8P3A1N1D2I1N1G2U1P3O1N1
1 + 8 + 3 + 1 + 1 + 2 + 1 + 1 + 2 + 0 + 1 + 3 + 1 + 1 =26 PTS
DOUBLE WORD → 52TRIPLE WORD → 78
MEANING

What does expanding upon mean?