A total event collapse was a time explosion which caused the universe to collapse totally, hence the name.
A total event collapse could be caused by a TARDIS exploding, as happened when the Doctor's TARDIS exploded. The Eleventh Doctor seemed to know of total event collapses and that the only way to stop one was to reboot the Universe. Some things could survive a total event collapse if they were at the centre of the explosion before they were also erased from existence, as happened with the Earth. (TV: The Big Bang)
The Doctor noted that every sun would "supernova at every moment in history" and that "the whole universe [would] never have existed". (TV: The Pandorica Opens) Though Earth's sun went supernova, Earth itself, at the "eye of the storm", survived longer as a meta-temporal event. From the Doctor's viewpoint, the Earth, the moon and the exploding TARDIS existed until 1996, when they too began to fade. Aside from the Moon, the exploding TARDIS, Earth and its inhabitants, every star, planet, life form and object was wiped from the Universe, past, present and future, across all parallel dimensions. Those races present near the initial explosion, namely, the Alliance, were preserved as stone statues. These species included the Daleks, Cybermen, Judoon, Hoix, Silurians, Roboforms, Sycorax, Sontarans, Zygons, Drahvins, Terileptils, Atraxi, Haemogoths, Slitheen, Blowfish, Uvodni, Chelonians, Draconians, Autons, Weevils and Nestene.
The Doctor reversed the total event collapse with the Pandorica, which contained a few billion atoms of the former universe. He flew the Pandorica into the heart of the exploding TARDIS, sending the Pandorica restoration field across every point in time, therefore restoring the universe. (TV: The Big Bang)
A total event collapse could also change some species' histories. A Cyber-Leader noted that "all universes will be deleted", which suggests a total event collapse also affected parallel worlds. (TV: The Pandorica Opens)