Sweeper can be Physical or Special
A Physical Sweeper is a Pokémon made to inflict massive physical damage, the fastest way possible. These Pokémon's stats concentrate on Attack and Speed.. Heracross, Tauros and even Charizard are good Physical Sweepers.
A Special Sweeper uses high Speed and Special Attack stats to blast its opponent with the strongest of special moves.. Alakazam is an example of Special Sweeper..
Hope it Helps! :)