Area Damage X: A cumulative, triggered ability that means, "Whenever damage from this unit's attack causes a unit in this arena to be discarded, this unit may do X dice of damage to another unit in this arena."
Double Strike
Double Strike: An isolated, static ability played after the attack end POP that means, "You may choose a unit that this unit can attack. This unit attacks that unit. Play only if this unit just attacked and only if it tapped for that attack." The unit must tap for the first attack, not the second. If it untaps, it may double strike again. Double Strike doesn't allow you to attack your own units.
INSERT
INSERT: A layered, static ability that means, "When this card is in play or stacked under the unit, the unit gets the following effect:" Insert works while in the build zone. The effect works while anywhere in the unit's stack. The granted ability remains to be the ability of its type. (For example, activated abilities granted by Insert may be disrupted.) The granted effect may not work in the build zone as per the rule for the rule for that effect.
Resilience
Resilience X: A cumulative, static ability that means, "As long as this unit has at least X damage counters on it, it gets +X power."