Watts are a series of monsters which have low ATK and DEF but can attack directly or have effects when destroyed or when they battle.
Watts are quite bad as they are slow, most effects of Watt monsters activate during the Battle Phase. Their Spell/Traps are quite lackluster but Wattrain is a good way to turbo out Watt monsters to go into Synchros, the Hunder family also help in this regard (You can also run Brohunder if you, for some reason, need more searchers) and Thunder Sea Horse and Pot of Prosperity allows you to search your Watts or Hunders.
This deck is also decent at stalling. If you're a Master Duel player, you can use 3 copies of Wall of Revealing Light, I suggest you replace Swords of Revealing Light with Wall of Revealing Light if that is the case.