What do the callouts "approaching minimums" and "minimums " mean?
The "Approaching Minimums" callout is made by the Pilot Monitoring (or, in some cases equipment, the GPWS -- Ground Proximity Warning System) as the aircraft is descending on an instrument approach and has reached an altitude 100 feet above the minimums for that approach -- the Decision Altitude (DA -- typically used for a Cat I ILS, and set as XXX' MSL) or Decision Height (DH -- typically used for a Cat II or Cat III ILS and set as XXX' or XX' on the Radio Altimeter) or Minimum Descent Altitude (MDA -- typically used for a nonprecision approach and set as XXX' MSL).  The response by the Pilot Flying is usually standardized and indicates he is looking outside in order to acquire the visual references he'll need to land.

The "Minimums" callout is made at the minimum altitude, and this is the point that the Pilot Flying has to make a decision -- continue or go around.  His response at this point is again standardized so that the other pilot is entirely clear on the course of action.  His response is usually something like "Landing" or "Continue", or else "Go Around."  Often, the autopilot comes off at this point as well &amp; you hear the horn indicating such on the CVR as well.