HGE

easy.

z-order and z-buffer both come from the same concept, ordering things by depth (z-axis). A z-buffer is like a 2D image, that's the same size as your whole screen. Each pixel in that image doesn't store color, but stores the Z value for that pixel (depth of the pixel away from camera). When you draw things using a z-buffer, hardware automatically compares each pixel you are about to draw to the corresponding z-buffer pixel, and actually draws the pixel if the z value is further away than the pixel. It will not draw that pixel at all, if the z value is closer to camera.

Without using a z-buffer, and just sorting things by depth (z-order), you cannot achieve specific results, like two intersecting triangles being drawn correctly. Say you have two triangles, and you draw one first, then the other one. THe latter one will always be ontop of the first one, because you rendered it after. So even if the two triangles intersect, the second one will draw itself on top entirely.

Using a z-buffer, you can get correct results from intersecting geometry. Also, you don't have to sort things out by depth, and just draw them in 3D space. Even if you rendered the second triangle after the first one, if the first triangle is closer to the camera, the second one will not overwrite the first one.

Hope this helps,
Also, you might want to www.google.com and find more details.

Understood. So this means u can create pseudo-3d objects using it correctly in HGE...right?

It means that you can create sprites with depth values, and that HGE will render them correctly no matter what order you actually render them in.