Default:

Rank when you spawn. You can't really do anything but use chat. You must apply to be promoted to Time Lord.

Time Lord:

You're a Time Lord. You can do basically everything including building a TARDIS.

Donor:

Like a Time Lord but awarded to donors. They get special features like World Edit.

Builder:

Like a Time Lord but you get World Edit and maybe Voxel.

High Council:

Basically like an Admin. You are like rulers, but must be good rulers.

Council President:

The Doctor. The Owner of the server. Can do everything and helps out a lot.