A triggered ability is an ability that starts with the words when, whenever, or at. These go on the stack automatically when their condition is met
So as far as strategy goes I would recommend getting this card on your bench as soon as possible so you can utilize its Poke-Power, also I would recommend getting 3 energy cards attached to it that way if you do have the same number of cards in your hand as your opponent you can switch it in and then use Extrasensory and then retreat it again next turn plus since this card is a normal type you can use this card in whatever deck you like and attach whatever kind of energy to this card, so I wouldn't necessarily recommend using this card for attacking, it is pretty decent, but I would definitely recommend using it on your bench all game long
I did build around him here in real life but that's not +1/+1 counter themed but Pingers and Dinosaurs with enrage instead
24 of these cards are also available as Quarter Century Secret Rares, and 1 special card is only available as a Quarter Century Secret Rare
Charizard's first attack requires three energies and deals 100 damage, which is already impressive for one attack
But these two are Bant counters creatures, and while they work really well together, I want to talk about their decks and what people are going to play