What is Charge in Hearthstone?
Hearthstone has many card effects that are common enough that they get their own keyword - a word or two that immediately tells you how the card works. Let's take a look at the Charge keyword.
Can attack immediately.
Charge is a keyword that means that the minion in question is unaffected by summoning sickness, and can attack as soon as it enters the battlefield (assuming it's your turn when it's summoned).
Charge can be used offensively or defensively, but its dangerously aggressive design with no counterplay has resulted in it being phased out in favor of Rush introduced in The Witchwood.
Keywords that Work Great with Charge
Divine Shield will allow a Charge minion to attack an enemy minion and stay alive to fight a bit more. Windfury can be used to deal extra damage or attack extra enemies.
Playing Against Charge in Hearthstone
Unfortunately, there is no direct way to play against Charge, which is part of why it has fallen out of favor in use. The few ways to indirectly play against Charge minions is to have Taunt minions or Secrets up.
Example Hearthstone Charge Cards
Stonetusk Boar is a basic representation of the mechanic is a simple 1/1 Charger for 1. Although it hasn't been a staple card in most decks for the majority of the game's history, it was a star-played in Quest Rogue with The Caverns Below. Blizzard in the past has also talked about how the card has limited design space.
Leeroy Jenkins is an iconic Charge minion that has been a staple finisher in Aggro decks since the game's debut and continues to be as such.
Warsong Commander is the only card in the entire game that specifically synergizes with Charge, and has had a very long and interesting history over the course of the game. In its original form, it was a 3 mana 2/2 that gave all your other minions Charge. When that proved to be too powerful, the effect was scaled down to only affect minions with 3 or less Attack, and its Health was bumped up to 3 to compensate. After Blackrock Mountain is released, it was part of a powerful combo with Grim Patron which had a very polarized reception between the Hearthstone community. In October 2015, it was changed to its current form where the card has merely been a shell of its former self. The card is largely useless as it loses too many stats for an effect with very small potential and support, and as of Rush ultimately replacing Charge, it's unlikely that it will ever receive future support again.