When you do, destroy all artifacts, creatures, and enchantments
You need two creature cards in your yard and one in play
Think of it like a Pokmon battle: you wouldnt send your Squirtle into a match without knowing its moves, and you shouldnt jump into selling without a solid strategy
Notably, while these Cids are the same card, you can have any number of Cid, Timeless Artificer cards within a single deck
On the card, this is depicted as a specific board wipe before the application of +1/+1 counters
This became a meme because there's a completely absurd battle animation which shows the character picking up the entire train to perform the move and slam it on its head - before, in some cases, the train can then be seen the right way up on the tracks