A Physical Sweeper has higher Attack
A special sweeper has higher Sp. Attack
A wall has higher HP, Defence and Sp. Defence
A tank has higher Attack, Sp. Attack and Speed
To be considered a Sweeper, you must also have high speed. A Tank will have high Defense and Attack for a physical tank, or Sp Def and Sp Attack for a special tank, but will not have high Speed unless it is upped in some way by a move or item.
Tanks are defense and offense, otherwise correct (Special Walls/Tanks Exist too)