Married/Divorced - 'Married' means the transfer case is bolted directly to the back of the transmission via an adaptor, whereas 'divorced' means the transfer case is separate from the transmission and is connected via a short driveshaft.
Full-time vs. Part-time - A full-time 4WD system provides engine power to both the front and rear axles on all surfaces at all times. This usually requires a transfer case with a center differential, a viscous coupling, or both. Full-time 4WD improves traction and handling on paved surfaces in inclement weather, but may reduce fuel economy.
A part-time 4WD system is designed to be operated only on reduced-traction surfaces. The transfer case lacks any mechanism to allow front-to-rear axle speed differentiation. Thus, any accumulated driveline bind must be released via tire scrub. Extended use of part-time 4WD on a high-traction surface, such as dry pavement, can adversely affect handling and damage the driveline. Some, but not all, part-time 4WD systems allow the operator to shift from two- to four-wheel drive "on-the fly."