How keyword abilities work in Magic: The Gathering — from flying to ward to double strike. — 14 questions answered.
Trample means excess combat damage carries over to the defending player (or planeswalker). If your 5/5 trampler is blocked by a 2/2, you assign 2 damage to the blocker (enough to kill it) and the remaining 3 damage hits the player. Trample only works in combat, not with direct damage spells.
A creature with flying can only be blocked by creatures with flying or reach. It's the most common evasion keyword in Magic. Flying creatures can still be targeted by spells and abilities normally — flying only affects blocking during combat.
Ward is a triggered ability that counters a spell or ability targeting the permanent unless its controller pays the ward cost. For example, Ward 2 means an opponent must pay an extra 2 mana to target it, or their spell is countered. Ward triggers each time, and the cost can be life, discarding, or mana.
Vigilance means the creature doesn't tap when it attacks. Normally, attacking requires tapping (which means the creature can't block next turn). Vigilance lets you attack AND still have the creature available to block, use tap abilities, or crew vehicles.
Double strike means the creature deals combat damage twice — once during the first strike damage step, and again during the regular damage step. This effectively doubles its combat damage output. A 3/3 with double strike deals 6 total combat damage. It also triggers 'deals combat damage' abilities twice.
Menace means the creature can't be blocked except by two or more creatures. This makes it harder to deal with in combat since the defending player needs to commit multiple blockers. Menace is strongest when your opponent has few creatures on the battlefield.
Lifelink means any damage dealt by the creature causes its controller to gain that much life. This applies to combat damage AND non-combat damage (like a lifelink creature with a 'ping' ability). Multiple instances of lifelink don't stack — you only gain life once per damage event.
Flash means you can cast the spell any time you could cast an instant — during your opponent's turn, in response to spells, during combat, etc. Normally creatures, enchantments, and other non-instant spells can only be cast during your main phase. Flash removes that restriction.
Reach allows a creature to block creatures with flying. Normally, only flying creatures can block other flyers. Reach gives ground-based creatures (like archers, spiders) the ability to block aerial threats. Reach does NOT give the creature flying — it can still be blocked by any creature.
Protection from [quality] means the permanent can't be: Damaged, Enchanted/Equipped, Blocked, or Targeted by sources of that quality (remember the acronym DEBT). For example, protection from red means red spells can't target or damage it, and red creatures can't block it. Protection doesn't stop board wipes or effects that don't target.
Haste means the creature can attack and use tap abilities the turn it enters the battlefield, ignoring summoning sickness. It's one of the most valuable combat keywords because it gives opponents no time to react. Red is the primary haste color. Haste matters most on high-impact creatures.
When you cast a spell with cascade, you exile cards from the top of your library until you hit a nonland card with a lower mana value, then you may cast it for free. Cascade triggers on cast, so even if the original spell is countered, you still get the cascade. Cascade is one of the most powerful mechanics in Magic.
Indestructible means the permanent can't be destroyed by damage or 'destroy' effects. A creature with indestructible survives Wrath of God, Lightning Bolt, and combat damage. However, indestructible does NOT prevent: exile, sacrifice, -X/-X effects reducing toughness to 0, or being bounced to hand. It's strong but not invincible.
Prowess triggers whenever you cast a noncreature spell, giving the creature +1/+1 until end of turn. Each noncreature spell triggers prowess separately, so casting 3 instants gives +3/+3. Prowess rewards spell-heavy decks and is strongest in Izzet (blue-red) strategies that chain cheap cantrips and burn spells.