before vitz i owned honda civic vti oriel manual 5 speed..
so im new to this CVT gear tranny too but whatever i knw im sharing
D = Drive
S = Sport (higher revs) / third gear tops
B = Braking (engine breaking) / second gear tops
It increases the use of the engine braking,Since this CVT has no gears to manually choose from, you need this to adapt to the individual situation 
and for personal experience to feel the difference b/w these gear drives
stick shift in D and drive at 40-50kmph in minor traffic/less traffic road
than shift it to S and B as u shift down u 'll gradually and respectively feel the difference in the drive on trio gears
hope my lecture
helped u
lol
i did 145kmp/h on B haha lol my dad scolded me he was siitting next to me he was like are u mad or what insane kid slow it down...and it was the first day he gave me the keys of this fantastic Car lol 