The Hearthstone meta consists of various types of decks keeping each other in check. Similar to the checks and balances of politics or the game rock-paper-scissors, Hearthstone decks have good and bad match-ups.
Control decks used to be viewed as incredibly boring to play and play against. In the early days of Hearthstone, everyone brought a control warrior list to tournaments and it would be turn after turn of “armoring up.” Plenty of more interactive and fun control lists exist, and they yield a pretty good success rate in most metas.
The goal of a control deck is to stall out the game until late-game through removal spells and weapons and draw cards until late-game comes and they can play their large, game-ending minions and spells. The trick to playing control decks is to strategically deal with your opponent’s early threats as quickly and efficiently as possible in order to set up for turn after turn of large, game-winning threats later on and completely outlasting your opponent.
Because control decks run mostly removal and large minions, it can’t really deal with constant threats of small and then medium minions of a midrange deck. Control and midrange are on equal footing early, but because midrange threats come out earlier, they out-tempo the control decks. If a control deck is teched with more removal for medium threats or with its own earlier threats, it can compete better with midrange decks, but after a certain amount of that teching, it becomes a midrange deck in and of itself.
The ability to make all of your opponents early pressure irrelevant with early AoE spells and taunt minions and keeping yourself alive with heals make control decks dominate aggro decks. If a control deck outlasts an aggro deck and can play its multiple large threats, the aggro deck will have no way to contest the board and might as well concede. If you are unlucky enough to draw your late-game minions early and not get the early removal you need in these match-ups, an aggro deck will finish you off before you can even complain about the draw.
Because control games take longer, they are a very slow and methodical deck to play. A lot of players enjoy this play-style, as it can be a lot of fun to have to analyze every turn, whereas an aggro deck player knows to just play every minion they can and hit face.
The original control deck was control warrior that played a few early minions for card draw and armor gain, weapons and spells for removal and a ton of huge minions with which to dominate the late game. Handlock was a popular control deck for a long time that utilized its card draw and low health to play large giants minions for low cost and Lord Jaraxxus or Alexstraza to keep surviving. The most recent group of control decks were the trinity of Reno Priest, Warlock and Mage that would control the and restore themselves to full health when times were tough with Reno Jackson. These decks have two things in common. They outlasted their opponents, and they played way more big minions and spells to finish the game.