This counts frames received on this interface that were under 64 octets and also failed their FCS or alignment check -- genuinely malformed runts, not just short-but-valid frames. Fragments are the textbook byproduct of a collision cut short mid-transmission or of a bad physical connection, so any count above zero for the current, still-accumulating short interval bin on what should be a collision-free, full-duplex port is worth treating as a physical-layer fault on this specific link. For example, FragmentsPkts reading 22 for this in-progress short-interval bin on a port that also shows rising TxCollPkts would tie the two together as one duplex-mismatch problem on that link.