All Wranglers come with strictly a part-time 4x4 system, a full-time 4x4 system is only available in the other Jeep models. The Wrangler shared its instrument panel with the now-discontinued XJ Cherokee so it also contained the full-time 4x4 indicator used (only) by the Cherokee. So that full-time 4x4 indicator is not used in the Wrangler, only the Cherokee.
Part-time is the more aggressive form of 4x4 when compared to the street oriented full-time type of 4x4 system. Part-time was designed for strictly offroad use or when the streets are 100% covered in something slippery like snow or ice. Wet roads don't count as being slippery enough, a part-time 4x4 system should not be used on paved streets that are simply wet from rain... streets that are simply wet have too much traction for a part-time 4x4 system.
A part-time 4x4 system mechanically locks the front and rear axles together so they are forced to turn at the same RPMs. Unfortunately, the front tires must be able to rotate faster than the rear tires during a turn and a part-time system wasn't designed to allow that. Offroad, that's not an issue since poor traction offroad surfaces allow the tires to slip & slide so the front tires can rotate faster against the dirt/mud/sand/etc. when they need to. When they can't, like happens on pavement, the steering bucks and jerks as the tires try to slip against a surface that has too much traction to allow that.
A full-time 4x4 system can be used on the street since unlike a part-time 4x4 system, it also includes a differential between the front and rear axles... exactly like is inside the axle between the left and right tires. The full-time 4x4 system's differential allows the front and rear tirs to rotate at different rpms like the left and right side tires are on an axle.
Hope that helps.