Silverfish are small, ground-based Hunter-Killers created by SkyNet. They are modeled after their namesake insect and with their high speed and small size, they are difficult to spot on the battlefield. They are designed to scutter into enemy command posts or behind enemy cover, upon which they explode and scatter schrapnel, skewering all nearby human combatants.
The H-K Silverfish was intended to appear in the opening battle of Terminator 2: Judgment Day but never made it into the finished film. It has only been mentioned in the T2: Nuclear Twilight comic and seen in the Terminator 2 illustrated screenplay.