According to Blizzard’s announcement, “If you’re new to Hearthstone and wondering where to begin, the Welcome Bundle will set you well on your way to building a Classic deck recipe or creating an exciting new deck of your own. You’ll unwrap one of nine Classic class Legendaries, such as the mystical Mage card Archmage Antonidas, or the relentless Warrior card Grommash Hellscream!”
These Welcome Bundles aren’t free, obviously, and are priced at $4.99, but as Blizzard said, it will net you one of the classic class Legendaries and 10 Classic Hearthstone packs, enough to get you started on your deck building. Blizzard also notes that existing players can also purchase the Welcome Bundle if they want and if they don’t already have some of the cards.
However Blizzard says that only one Welcome Bundle is allowed per account, so don’t think you’ll be able to start hoarding them. The Welcome Bundle should already be live so fire up Hearthstone if you’d like to get your hands on it.