Rocker pertains to the arc of your board. This affects the way the board rides on the water as well as how it "pops" off the wake.
Here are the types of different rocker lines: Continuous - A continuous arc from the tip to the tail of the board Three Stage - The belly of the board is flat and the tip and tail kick upwards. Blended - The edge of the board has a continuous arc while the middle part(between the edges) flattens out in the belly.