Invert image flips the image from top to bottom, to compensate for ceiling mounting a projector upside down. Projectors typically ceiling-mount upside down, because most have "keystone" correction built in to compensate for the distortion created by "pointing up" from the table to the screen. Usual positioning has the projector about even with the bottom of the screen in a "table top position," or, even with the top of the screen when ceiling mounted.
Electronically flips the image from top to bottom, to compensate for ceiling mounting a projector upside down, as most projectors have "keystone" correction built in to compensate for the distortion created by "pointing up" from the table to the screen. The image must be inverted when the projector is hung upside down from the ceiling. Most projectors are operated with the lens about even with the bottom of the screen in a "table top position", or even with the top of the screen when ceiling mounted.