And more about this on the Nikon website:
In relation to D800 vs D800e:...Anti-aliasing filters are incorporated in the low-pass filter to reduce the effect of aliasing and moiré patterns that can occur in digital images. Aliasing and moiré patterns are more noticeable with subjects that include high-frequency (finely-detailed) patterns. A side effect of incorporating an anti-aliasing filter is that it reduces resolution within the image. Removing the anti-aliasing properties from the low pass filter results in improved image resolution, as the light is transmitted without being filtered through the lens onto the photodiodes in the image sensor. All other D800E functions and performance are the same as the D800; colour reproduction characteristics, infra-red coatings, anti-reflective coatings and image sensor cleaning functions are the same on both cameras. ...
On Nikonimaging nps I found a nice diagram to explain better: