The series is the baby of Hideaki Anno, it was produced by GAINAX in 1995. It features 26 episodes. The Last 2 episodes spouted much controverse across the fandom for their unusual graphic (almost psychedelic) style and the conclusion to the series storyline - which many didn't understand right away (neither do I).
The episodes 25 and 26 were later remade, new material was added and the result were 2 movies, namely Evangelion: DEATH & REBIRTH and The End of Evangelion.
This movies show a much more explicit version of the End of Evangelion
There are well over 100.000 Neon Genesis Evangelion sites out there, every flavour of explanation can be found, so I won't claim that I found THE explanation to NGE. Anyway, enjoy my pages ...