Render Size:
    For formats that allow you to specify the size of the output image when they are rendered. 

Include Header:
    For certain export formats, this will allow you to specify a file whose contents will be copied to the top of the output file, immediately preceding the scene information written by the program.

Include Footer:
    For certain export formats, this will allow you to specify a file whose contents will be copied to the bottom of the output file, immediately following the scene information written by the program.

Include Lights:
    For certain export formats that include ligting information, you can check this box to have that information included in the output file or not.  An example of when you might want to leave this item unchecked is when you've set up specialized lighting in an included header file which you want to use instead of the scene's lighting.

Include Camera:
    As with the Include Lights option, you can check this box to have camera information included in the output file or not, for certain file formats which allow for camera information.  An example of when you might want to leave this item unchecked is when you've set up a specialized camera in an included header file which you want to use instead of the scene's camera.

Override Material Names:
    A situation where you might use this option is when you're writing to or rendering via a rib file.  The rib file exporter uses the material names as the surface name parameter, and checking this option allows you to use the name provided in this field for every material instead of using the names of each material.  Thus, if you wanted everything rendered in a toon style, you could provide the name of your toon shader here and that shader would be used in conjunction with the different material colors to render everything in a toon-shaded style.