EVA-01 TEST TYPE. The first
Eva to be introduced to actual
combat, and the second
Evangelion built at
NERV HQ after
Eva-00. Although it plays a major role in many battles against
Angels, it also exhibits a number of unaccountable
phenomena, such as going
berserk, activating without an
entry plug inserted, and remaining active after its operational time limit, etc. In the battle against the 14th
Angel, it devoured the Angel and thus directly obtained an
S² Engine.
Purple in colour, its dedicated pilot is the Third Children - Shinji Ikari. It seems that the soul of his mother - Yui Ikari -- was made to dwell inside Eva-01. Also, the physical body of Eva-01 was apparently created from Lilith. This is why when the Lance of Longinus was lost, Eva-01 became the sole substitute for Lilith as the medium for Instrumentality (Human Complementation).
Source: The End of Evangelion : Glossary contained within The End of Evangelion - Theatrical Program.