Until end of turn, that creatures controller may play that card and they may spend mana as though it were mana of any color to cast that spell. Trample plus card draw and stealing stuff is a dream come true and we love this card so damn much
And because of the size of the format, it becomes easy to take advantage of stock decks
The drawback however is that they must be sacrificed at the beginning of your next turn
That was something more in red's part of the color pie, and it gave a secondary purpose to all the tokens you made
The most famous example is the easy infinite Zirda has with either Basalt Monolith or Grim Monolith untapping a Monolith isnt a mana ability, it just happens to control how often we can use the attached mana ability
Land Land (CTRL to add secondary) Ramp Kinnan, Bonder Prodigy Whenever you tap a nonland permanent for mana, add one mana of any type that permanent produced