A differential GPS module is used to achieve centimeter-level accuracy in your positioning solution. This higher level of accuracy is often required for critical applications such as surveying, mapping, and construction. A differential GPS module receives corrected information from a nearby reference station, which helps to remove errors introduced by the natural variations in the satellite signals and the environment.
Differential GPS eliminates pseudorange errors, which are distance discrepancies and signal delays between a GNSS receiver and a satellite. Although the fundamental functionality of GPS and differential GPS is the same, the former has a global range while the latter has a local range. Moreover, differential GPS modules are more expensive than their GPS counterparts.