These two decks share the same idea, are quite similar and sometimes use the same cards so we'll bunch them together here. The idea is to reset the counters on the creatures Triskelion and Tetravus, so you'll be able to swarm the board with 1/1 creatures or just shoot the opponent in the face for a lot of damage.
Coffin Combo utilizes Tawnos Coffin for this purpose as it remembers the amount of counters on the creatures it exiles. Therefore, the creature returns with both three new counters and the ones it had when it was exiled.
The Machine instead uses Hell's Caretaker to reanimate the creatures over and over again and use the counters on them between each repetition. That's about it. The rest is up to you!