You take two piles of cards (probably halves of your deck in smaller deck formats) and push them together so the cards interweave
They can be extreme deadweight in your hand if you cannot cheat them out, so it's very important to jam some artifact cost reducers into your deck such as Foundry Inspector and Cloud Key
Great spot and safe area
Sacrificing a bunch of tokens to give a huge power boost to a single creature opens up a new axis of attack especially in token decks
While there are a few other possible options, they feel less likely due to power level or complexity than everybodys favorite giant killer zombie
Your deck wants to ramp heavily, try adding a balance of early game ramp that costs 2-4 CMC and late game ramp that costs 5+ CMC, some good early ramp options include Farseek , Rampant Growth , Grow from the Ashes , Skyshroud Claim , Circuitous Route , Myriad Landscape , Burgeoning , Blighted Woodland