The impact theory involves a strike by a rogue Mars-sized planet. The transfer of kinetic energy would have liquefied Earth and splashed a quantity of the magma into orbit, which would coalesce into the orb of our future moon. Any water would have to have been vaporized, but seemed to have remained within the splash itself, thereby mingling with the igneous stone.

There are also thoughts that Earth-life may already have formed, only to have been annihilated with the impact. There is currently no known way to find any of this out for certain.

An advanced civilization?
Microbes?
Simple sea life?
Completely unknown.

Incidentally, the Moon's rotation is currently tidally locked to the Earth's, so that one side faces it at all times. The Earth's rotation, though, is continuing to slow, until one day in the far-flung future, possibly before our sun becomes a dying red giant, planet and moon will be locked to face each other.

Fascinating dynamics.