TrainingTraining is a triggered ability. “Training” means “Whenever this creature and at least one other creature with power greater than this creature’s power attack, put a +1/+1 counter on this creature.”
If a creature has multiple instances of training, each triggers separately.
Some creatures with training have abilities that trigger when they train. “When this creature trains” means “When a resolving training ability puts one or more +1/+1 counters on this creature.” (CR 702.149) (Whenever this creature attacks with another creature with greater power, put a +1/+1
counterTo counter a spell or ability is to cancel it: remove it from the stack without resolving it. A counter on an object or player is instead a marker that changes characteristics or interacts with rules or abilities; for example, a +1/+1 counter modifies a creature’s power and toughness. (CR 701.6; 122.1) on this creature.)
When this creature
diesIs put into a graveyard from the battlefield. (CR 700.4), put its
countersTo counter a spell or ability is to cancel it: remove it from the stack without resolving it. A counter on an object or player is instead a marker that changes characteristics or interacts with rules or abilities; for example, a +1/+1 counter modifies a creature’s power and toughness. (CR 701.6; 122.1) on target creature you control.