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.)
Whenever this creature trains,
exileTo exile an object, move it to the exile zone from wherever it is. See rule 406, “Exile.” (CR 701.13) up to one other target creature from the battlefield or creature card from a graveyard.
When this creature leaves the battlefield, put the exiled cards onto the battlefield under their owners' control.