Time Vortex
The Time Vortex is the place through which the TARDIS travels. With the Time Vortex, someone could conceivably reach any point in time or space (though the Time Spiral could cause some problems in the trip). Other space-time vessels, such as those used by the Daleks (DW: The Chase, The Daleks' Masterplan) use the Vortex, though not nessecarily all of them.
Still, access to other universes remains somewhat more difficult. (DW: Inferno, Rise of the Cybermen).
Native life in time vortex includes the Reapers ((DW: Father's Day) and the Chronovores. (DW:The Time Monster)
Mrs Wormwood detected artron energy in her scan of Sarah Jane Smith, using it to conclude that she had travelled in the Vortex. (SJA: Invasion of the Bane)
- We do not know if she had residual artron energy as the result of travel through the Vortex itself or as a result of her means of travel, namely the Doctor's TARDIS.
Note
The Time Vortex apparently looks like the title screen on the series, specifically the title for the new series.