Chiropractic mobilizations refers to low velocity movement and stretching of the muscles and joints, with the goal of increasing the range of motion within those areas.  The joint stays within its passive range of motion.  The difference between mobilization and manipulation (an adjustment) is that manipulations are quicker, controlled thrust that takes the joint or tissue beyond its typical range of motion to alleviate pressure quickly; mobilization is a gradual movement where the tissue is slowly adjusted to reduce tension.