Six degrees of freedom (6DoF) refers to the freedom of movement of a rigid body in three-dimensional space. Specifically, the body is free to change position as forward/backward (surge), up/down (heave), left/right (sway) translation in three perpendicular axes, combined with changes in orientation through rotation about three perpendicular axes, often termed pitch, yaw, and roll.
This is something that will be crucial to any future plans of VR, AR and MR.
As a CGI artist I am fluent with navigating myself around a 3D space using a Wacom pen and a combination of customised button control and use of the ctrl/alt keys. But I was myself unfamiliar with this terminology which seems to be at the core of much development at the moment.
Obviously 360 video cannot provide full 6DoF so will naturally settle itself as different kind of medium.