Macro lenses are used in applications when the object size is approximately the same as the size of the camera sensor (between 10x smaller to 10x larger).  They are very low distortion and offer superior depth of focus than general purpose lenses but not as much as telecentric lenses.  Most macro lenses have a fixed working distance and often have no moving parts making them ideal for industrial applications where unwanted adjustments could cause problems although there are also zoom models available.

F-mount macro lenses are used when C-mount lenses are too small (with sensor sizes exceeding 16-20mm).