This reports the discovery state of the blade currently occupying this slot — where it stands in being inventoried by UCS Manager. For this chassis slot's endpoint for whatever blade currently occupies it, discovery tells an admin whether a newly inserted blade has finished being scanned and its hardware inventory (CPU, memory, adapters) fully catalogued, which is a prerequisite before that blade can be associated with a service profile. Right after reseating a blade, this would read something like 'discovery-in-progress' before settling to 'complete' a few minutes later once UCS Manager finishes the scan.