Crucible Data

I'm looking at Crucible data for a school project (how I convinced my professor that was okay I'm still not quite sure) but I've run into something I don't fully understand. For each player there is a list of how many kills they received with each weapon. For example there is[i] weaponKillsGrenade, weaponKillsSniper[/i], and[i] weaponKillsPulseRifle[/i]. The one that I don't understand at all is [b]weaponKillsRelic[/b]. I've been focusing mainly on Control data too, so I'm not sure what weapon kills count towards this category. If anyone has any insight please let me know!