A gambler who is defined as a agro type is generally an aggressive gambler. To be more specific, it is a player who will tend to favour aggressive actions in poker (bets, raises, check-raise, all in, bluffs), rather than passive actions (pass, lying down, giving up one's hand easily). aggro-type players are probably the most formidable opponents since they will never give us an easy ride. They are the ones who will be able to make a very wide check-raise to flop, who will be able to bluff often. Against this type of player, we can expect a lot of variance.
Player aggro vs passive
All good poker players agree that a winning poker is an aggressive poker. You don't win pots by laying down all hands. And you win bigger ones by being aggressive. At poker, good hands are rare. Simply waiting for your hand will not be enough to win in the long run. By being aggro, you win undisputed pots. For example, in a hand, if two players don't have good cards, the most aggressive player (aggro) will win the pot.