Projector AR confusion

[Marty2003]

I'm thinking about getting a projector and from reviews I'm considering a BenQ PB6200. It's native resolution is 1024x768. For the aspect ratio it's listed as 4:3 native\16:9 selectable. What exactly does 16:9 selectable mean? I figure it either means it has a way of anamorphically stretching the XGA resolution, or it masks part of the "square" 4:3 image.
So if 16:9 mode is selected does the resolution stay at 1024x768 and each pixel becomes rectangular, or does it simply turn off some of the pixels so the resolution actually becomes 1024x576?
If it's the latter, would there really be any benefit to using 16:9 mode, rather than displaying a 16:9 source in 4:3 mode?

[BJ_M]

masks part of the "square" 4:3 image in 16:9 mode ..

for best 16:9 , buy a anamorphic lens adaptor for that projector ..

[Marty2003]

Thanks for the reply. You just made me realize why DVD players can output video in their vertically compressed anamorphic AR I always wondered who could possibly watch a movie like that