The Birds come down a turn earlier, require fewer colors to play, and generate any color of mana when they tap instead of just black
Five-color decks probably dont have a need for something like this since they have access to every other card Commander has to offer, but running this in some two-colored archetypes that may not run a lot of refill options, like Boros, could also be a good shout
It is not just your commanders colors, it includes mana symbols on the card, too
If you have just a Grizzly Bears, it draws you three cards and is a 3/3 creature
Proxy cards are copies of real cards used as substitutes
Rinse and repeat until you are satisfied