AffinityAffinity is a static ability that functions while the spell with affinity is on the stack. “Affinity for [text]” means “This spell costs less to cast for each [text] you control.”
If a spell has multiple instances of affinity, each of them applies. (CR 702.41) for creatures (This spell costs
less to
castTo cast a spell is to take it from the zone it’s in (usually the hand), put it on the stack, and pay its costs, so that it will eventually resolve and have its effect. A player may cast a spell if they have priority. See rule 601, “Casting Spells.”
To cast a card is to cast it as a spell. (CR 701.5) for each creature you control.)
VigilanceVigilance is a static ability that modifies the rules for the declare attackers step.
Attacking doesn’t cause creatures with vigilance to tap. (See rule 508, “Declare Attackers Step.”)
Multiple instances of vigilance on the same creature are redundant. (CR 702.20) (Attacking doesn't cause this creature to
tapTo tap a permanent, turn it sideways from an upright position. Only untapped permanents can be tapped. (CR 701.26).)