Hi Michelle- I can see how you might be confused about the two-
CreaseSplitting controls whether new surfaces with creases are split into polysurfaces at the creases,or not. Default = Split, it is uncommom to want to keep kinked surfaces as single surfaces. It can happen that this will get set to No by a plug-in, and cause all kinds of confusion for users- T-Splines was a prime suspect for this in the past.
DivideAlongCreases acts on creased surfaces to split them into polysurfaces at the kinks.
-Pascal