With Standard mode, the front/rear split varies depending on conditions; most of the time, the Cherokee should stay in front wheel drive for better gas mileage.
Sport limits traction control, increases stability-control slip thresholds, changes the torque bias for better cornering, and allows a target front/rear torque split of 40/60 for a rear-drive feel.
Snow starts in second gear, sets brake controls for slick surfaces, and goes into full time 4x4, preferring a 60/40 front/rear split.
Mud/Sand is similar but uses off-road brake controls, and a preferred split of 100% rear wheel drive.
Finally, Rock, on Trailhawk only (and requiring 4x4 Low), is similar to Mud/Sand but increases brake lock differential capacity and locks the differential.
Above is taken from http://www.allpar.com/SUVs/jeep/2014...#ixzz2kelsAU2T