Summoning Sickness is an old game term to describe the inability of creatures to attack or use activated abilities with the tap symbol in them on the turn they come into play (and the following opponent's turn). Although all permanents experience Summoning Sickness, only creatures and artifact creatures (or land, artifacts or enchantments that have become creatures) are affected by it. Creatures with Haste do not suffer from summoning sickness - they can attack and tap on the turn they come into play; in fact, instead of the term 'Haste', cards used to say, 'does not suffer from summoning sickness'. Note that summoning sickness only affects abilities with the image in the ability. If a card requires you to tap creatures, but does not do so with the tap symbol, summoning sickness does not prevent that effect. For example, Convoke and Selesnya Evangel's ability can be used with creatures with summoning sickness.