The Void

The Void was the emptiness between universes. The name "The Void" was only given to it by the Time Lords. It was also known to the Eternals as "'the Howling", and to others as "Hell".

Rassilon was (amongst other titles) "Ravager of the Void". (BFA: Neverland)

It contained no temporal or spatial dimensions, but a language which might have been used to conceptualise it. For example, the Doctor confirmed that the Void had no 'up' or 'down', but also talked about the universes within it being 'stacked' on top of each other. Even "time" in most senses, didn't actually exist there. (DW: Army of Ghosts) If someone travelled through the Void, they would have absorbed background radiation, which the Doctor called Void stuff. (DW: Doomsday)

Void travel
A Void Ship was a spaceship which could travel through the Void into other dimensions. While originally believed to be only theoretical by the Time Lords, it was eventually discovered that the Daleks were in possession of a powerful Void Ship in the form of a golden sphere. (DW: Army of Ghosts)

The Cult of Skaro travelled to the Void to escape from the impending destruction of the Dalek Empire in the Last Great Time War by the Doctor, taking with them the Genesis Ark, a prison ship containing millions of Daleks, and hid in the Void until the time was right. (DW: Doomsday)

This Void Ship caused a crack in the universe, making travel from one dimension to the next easier, allowing both the Doctor's TARDIS (not a Void ship) to travel to the dimension of the parallel Earth Cybermen, and those Cybermen to travel to the dimension of the Doctor. (DW: Rise of the Cybermen, Army of Ghosts)

As the Battle of Canary Wharf raged throughout London, the Doctor opened the breach of the Void, which sucked all of the invading Cybermen and Daleks into it (DW: Doomsday). The actions of other Daleks later weakened the dimensional walls, allowing some the Cybermen to escape the Void. The rest, along with the Daleks, perished, according to the Doctor as a result of the events surrounding the Reality Bomb. (DW: The Next Doctor)

When the Eleventh Doctor was for a time erased from existence by stepping into the cracks, River Song described him as being condemned to the Void between worlds. (DW: The Big Bang)

Other information
The memory changer "Adam Smith" said he had been trapped in the Void for a long period of time. (TW: Adam)
 * It is not confirmed if this was the same 'Void'. If not it may be the White Void.