A performance verification compares an instrument to a set of traceable standards and checks whether the instrument meets its published specifications.  The resulting performance verification is either a “PASS” where everything is in specification and no adjustment is needed, or a “FAIL” where measurement(s) are out of specification and an adjustment (or in extreme cases a repair) is required.
A calibration is a more comprehensive process that includes one or more performance verifications plus any required adjustments to ensure the instrument is returned to the customer with all measurements within specification.