This refers to a vehicle setting around tire pressures. Options are Light Load and Normal Load. Light Load is recommended for up to three persons typically in the vehicle, Normal for more than 3 passengers plus weight from cargo.
What it actually does is change the tire pressure setting at which the system will alert you to low tire pressures. Light Load allows you to run lower pressure in your tires (many run around 34-35psi cold) which will generally equate to a more comfortable ride. Normal mode and tire pressures around 44psi which really translates bumps to the cabin.