Also known as alpha access, alpha founding, game preview, and paid alpha, early access is a method of funding a game in different stages of development. Those who pay for early access are allowed to download and play the game in its early development. Some developers may also give those who have paid for early access the option to provide feedback and other bonuses after the game is released.
For example, Minecraft was an early access game during its development starting in 2009 and allowed Markus Persson to quit his full-time job to focus on it. Early access games gained popularity when Steam launched the Steam Early Access feature on March 20, 2013.
Keep in mind that if you do early access, you're not buying the entire game, as it's still in development. Often you're only purchasing parts of the game.
Do I have to purchase the game when released?
Early access is essentially purchasing the game early. You're paying for the full product ahead of time to play it early, so you don't need to purchase the game again once it is released.
If anything happens during development that causes the early access game to fail, you don't get a refund.
How long does early access last?
There's no limit to how long a game can remain in early access. Sometimes, games can remain in this stage for years.