If you're one of those people that always skips to the end of a book to find out the ending, then the read ahead ability is perfect for you. A Saga with the read ahead ability lets you choose which chapter it starts on. It enters with that many lore counters, and only that chapter ability triggers after it enters the battlefield.

Stun counters were introduced in the Dominaria United release. They're a special kind of counter that stops tapped permanents from untapping.

Kicker is an optional additional cost. As you cast a spell with kicker, you choose whether you're just paying the mana cost to get the spell's normal effects. If you have the mana available, you can choose to kick the spell, paying the mana cost and the kicker cost.