Warp
The Warp is an immaterial dimension of Energy, Emotion and constant change, it is home to strange beings and landscapes that would be considered dreamlike or nightmare like depending.
It flows like an ocean filled with rivers, constantly changing flows of energy currents, it is a place where thought can be made reality.
The Warp interacts with many different realities by does not always connect them except for a few instances, however thoughts may travel the bounds of time and space and existence in here.
All psykers draw their power from this realm, and New Covenant Vessels use it to let them efficiently travel Faster than light speeds, though time spent in the warp is generally exponentially longer than the time it takes to travel, so what seems like a jump that took a few hours or a week or so can act in the warp as weeks or months. However no biological aging occurs (Though their are exceptions, mostly in those who are born and live and grow up on ships, however there seems to be a point where growth during warp travel stops and only occurs in real space, this seems to be immediately after full development) during the travel, and so this may be seen as beneficial military wise as on board troops have time to train and prepare for an engagement, making New Covenant troops appear well prepared even though they may appear to not have had time to train.
The Warp Connects with all life, regardless, except for Blanks who have no presence in the Warp. It is not known why this occurs as it does not affect anything or grant psyker powers to those without the Mutation, or lack the capability even with the mutation. The only affect it has is that the actions of those in the Material world, their thoughts, dreams, ambitions, nightmares, and other emotions affect the warp and its flow. Dreams of a sleeping person can manifest themselves as a reality in the warp, and so can nightmares which can explain some of the strange entities of the Warp that are not solely Demonic in Origin though the New Covenant would treat them as such if they were ever encountered.
The Warp is currently only used for travel by the New Covenant and their Demonic enemies.
Warp Web
The Warp Web is new artificial construct engineered in the Warp by the New Covenant. It serves as a highway that connects to various points in galaxy through Gates placed in the Material Universe, the Dimension which all the other Empire exist in. It can serve as an escape for vessels as well who can retreat to it at will, though this Web can only be used to travel if a gate has been established in the target destination, but the Web can be accessed from any point in the Galaxy as long as the ship has the correct systems to do so, and the destination is either in the web or has a gate.