A minion that entered the realm this turn, whether from being cast or from another card's effect, suffers from summoning sickness until the end of turn. A minion suffering from summoning sickness cannot tap, or be tapped, to pay for costs associated with any ability. This includes any additional abilities that may have been granted by spells and artifacts. When you summon a minion on your turn, it enters play untapped, so you may use it to defend on your opponent's turn.