Hearthstone [official site] is getting some major changes thanks to a new format which restricts the cards you can use in your deck. The idea is the make for a more varied and interesting metagame as well as making competitive play more approachable for newcomers. More on that after the jump but one of the side-effects is you'll also be able to unlock double the number of deck slots so you can have up to 18 pre-made decks on hand for battle.
Okay, so. Hearthstone is getting split into two formats when the 2016 spring expansion arrives. One is called Standard. In Standard you can use any card released in the current and previous year as well as any basic or classic cards. When the first new expansion is released each year every set of cards that wasn't released that year or the year before will be removed from Standard play.
The other format is Wild where you can use any of your cards. Wild is what Hearthstone has been up until this point.
The change has come about because the more cards get added to Hearthstone the harder it is for those cards to have an impact on how the game is played. At a certain point you get this "solved problem" situation where most people just end up playing particular cards and particular deck variants because they're stronger and it doesn't make sense to play anything else. The whole thing stagnates.
The sheer volume of cards you can play with or come up against can also be offputting to new players. As lead designer Ben Brode puts it, "It's getting more and more daunting for new players to jump into the game. Also the cards we design have to compete with more and more cards making it harder for us to really shake up the metagame when we release new content."
With Standard format the idea is that you have this core of basic and classic cards which form the foundation of Hearthstone and then other cards are added via new expansions or adventures then removed after two years. Keeping the number of cards smaller and having that impermanent element means being better able to alter or disrupt the current metagame of Hearthstone.
Standard format will only be available in casual and ranked play in Play mode, Friendly Challenges and maybe some Tavern Brawl stuff in the future because the rules for the latter change from week to week. For everything else - Arena, Solo, Adventures... it's all Wild by default. You can use any cards.
The naming is interesting here. "Standard format" makes it clear that this is the version of the game Blizzard want as the default form of competitive play. They've also made it the form that will be used in official esports tournaments run by Blizzard like the Hearthstone Championship Tour and the Hearthstone World Championship in 2016.
Wild is so-called because "Eventually there will be tons of cards and it's going to get at little bit crazy". I'm inclined to disagree with Brode on this point. It will have a lot more cards but I simply don't see it being wild in any way, it'll just be that solved problem with dominant decks that don't really ever go away and a number of best cards/deck variants it doesn't make sense to stray from.
I'm interested in the change because the last few times I've written or commissioned articles about Hearthstone it's seemed to have a relatively stagnant meta. Maybe an expansion would arrive and upset a few things but after a week or so the decks would get figured out and it would be business as usual. Prioritising Standard mode will perhaps see more variation, particularly in terms of pro play.
To make room for extra dedicated Standard decks there are more deck slots. If you've unlocked all nine characters you'll now get nine more deck slots - 18 in total. You can divide them however you like between Wild and Standard.
There's a whole heap more information over on the Hearthstone blog which answers most logistical questions.