Jackal (Kig-Yar human name) are a species of "bird-headed pirates" who command massive starships and feature contraband around the Covenant.
They are weak, and use Point Defense Gauntlets that act like wrist shields, though they are not the strongest thing the Covenant ever made. The colors for the Shields are blue (Minor Jackal) or purple (Major Jackal). Jackals named "Sniper Jackals" are the Covenant's primary marksmen, often armed with Carbines or accurate Beam Rifles.
Jackals, as Samuel-034 noted, sure "aren't as tough as their ships", that can mean their commanded very powerfully armed starships.