Alpha Testing is simply a phase of the game in which certain parts of the game are presented to anyone who wishes to test it. Alpha Testing is not the full version, and has some of the defaults cut back.

For Instance, The max level cap for Alpha Testing is 40. In Alpha not every aspect of the game will be presented, there will be bugs etc. Also the first Landmass, Orion will not yet be finished.

These are expectations for Alpha. Beta will be a lot larger.