Sweeps are the minions of Scourge created by Unicron. Sweeps are visually indistinguishable from Scourge himself, although Sweeps do not necessarily have identical voices. While only a few are seen initially during Unicron's threat, there appears to be an inexhaustible supply of them later on. That's actually a good thing, as Megatron tends to shoot them.
Like, all the time.
Only three Sweeps have been graced with defined personalities and identifiers, namely Sweeps Two, Six and Seven.