Omniverse

The Omniverse or the All was the totality of all of existence, every individual multiverse. Although in this terminology "a multiverse" was a smaller grouping of universes within this totality, (COMIC: The Glorious Dead) the phrase "the Multiverse" was also often used to mean the totality of parallel realities, rather than a particular grouping of them. (AUDIO: Palindrome, Restoration of the Daleks, et al.)

Structure
The Time Vortex of the Doctor's own multiverse merged with the omniversal spectrum at the Glory, a device at the spectrum's focal point that maintained the structure of the omniverse as long as there was a living consciousness to direct it. (COMIC: The Glorious Dead)

The Sixth Doctor explained that while travelling the omniverse, time was relative and so "urgency" and "lateness" were non-existent where time travel was concerned. (AUDIO: Paper Cuts)

The Seventh Doctor called the Silurian Earth reality an unnatural branching of the omniverse, artificially created as opposed to Arthur's World which was natural. The Guardians of Time were one of the powers of the omniverse who could do anything, bound only by laws of conduct. (PROSE: No Future)

The omniverse consisted of infinite dimensions, and Lampreys were capable of devouring entire multiverses within the omniverse. (PROSE: Spiral Scratch)

History
In 2009, Davros and the New Dalek Empire took 27 planets, including the Earth, from their spaces in N-Space and placed them in the Medusa Cascade. They plotted to use the planets as a vast transmitter for their reality bomb, which would totally destroy every atom in the universe. However, the bomb's wavelength would also break through the rift at the heart of the cascade, meaning it would spread to every universe. As Davros and the Supreme Dalek explained, the bomb would destroy all of existence itself, leaving the Daleks the sole life forms in all of reality. Their plan was ultimately stopped by the efforts of the Tenth Doctor, his Meta-Crisis self, and the Children of Time. (TV: Journey's End)