I wrote this as a companion for a Hearthstone Arena guide. So if you stumbled upon this randomly, then give that a go.
Netdeck – When you copy a deck directly from an online resource. Don’t be ashamed, everyone does it.
Draft – The part of arena that starts by picking a class, and then all thirty cards.
Board control – The art of being in control of the board, and as such, the game. It’s more of a concept, so defining it is tough, but in essence, you want to be able to kill an opponent’s minions before they can actually do anything with them while they’re still sleeping.
Trading – When you attack one minions with one or more other minions, killing everything off in the process. 1 for 1 trades are best, but sometimes you have to do what you have to do, and 2 for 1 trades happen.
Card quality – How good a card is. A lot of time this has little to do with rarity. A lot of commons are the best cards in the game, and a lot of epic cards are just plain bad.
Curve – In Hearthstone, curve always refers to concerns of mana. When drafting, your curve is the overall mana cost of your deck, i.e. that bar graph in the top right. While playing, curve relates to the turn. You generally want to spend all your mana on each turn, and you generally want to play minions of the correct mana cost for the turn, e.g. a 4 mana-cost minion on turn 4. Having minions of increasing mana cost allows you to “curve out” well.
Value – Getting the most out of a card by either successfully using its Battlecry, deathrattle, or any other effect it has. Killing off a minion and surviving can also give a minion “value,” or if you buff a cheap minion in order to kill off a bigger one.
Combo – Using two cards in conjunction with one another for great effect. The example in the article is using Auchenai Soulpriest in order to make the 1 mana-cost Flash Heal deal 5 damage instead of heal 5 life. A lot of cards combo well with each other, and Rogues have an entire mechanic built around it.
Go Face – Using your minions to deal damage directly to the hero instead of trading into other minions on board. This is generally frowned upon as poor play, but there’s always a time to go face.
Lethal – Simply put: when you can kill your opponent and win the game.
Board Clears – Cards that can clear your opponent’s board, and sometimes your own. Most of them are spells such as Flamestrike, but minions can also be board clears, like Ravaging Ghoul, Dread Infernal, or Corrupted Seer.
Positioning – Where on the board you place your cards. This can be important to play around some of your opponent’s cards, and to get the most value out of your own.
Rope – When you rope on a turn it’s when you wait till the very last second to play.