Creatures you control have
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 a creature you control 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 the creature with lesser power.)
At the beginning of your end step, if you control a creature with 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 it that attacked this turn, draw a card.