Aramandur: When you purchase a game in Early Access you also get the final release of the game.

falloutttt: You get to play during the early access and once the game is released as well.

In some cases, game/s can even go up in price during the early access or at the release of the game. But you still own the game even if you paid less for it in the beginning stage.

Early Access is basically to support the devs (usualy small dev team with low budget) and test the game and possibly introduce some ideas for the game that devs may like and implement into the game.

At least that's how I see it.