Definition
Active sellers are the individual partner sales reps who are actually selling a vendor's product in a given period. This number is usually much smaller than the total count of signed partners or trained reps. Many channel teams track it because it shows real selling capacity better than partner count does.
Programs define active in different ways. Some count any rep with a registered deal or open opportunity. Others require a closed sale within a set window. Pick one definition and use it the same way every quarter.
A long partner list can hide a small group doing most of the work. Tracking active sellers helps a channel manager see where to focus enablement, recruiting and support.
In practice
A partner has 30 trained sales reps, but only four registered a deal last quarter, so the channel manager plans deal reviews with those four and a refresher for the rest.