Auto Reflection makes materials reflective by using a matching word pattern method in the material name. The reflection values for intensity, sharpness, index of refraction, and bump are preset, so reflection values for materials do not have to be individually set.
For example, you can specify that all material names that match the pattern "steel" will be 90% reflective and metallic.
Any assigned materials with names that match the list of patterns, and for which you have not already set specific reflection values, will render with the preset reflection values from Auto Reflection.
(If you do set reflection values for an assigned material, your settings will override the Auto Material settings.)
Resume Rendering lets you continue a rendering which has been completed - either because the number of passes or rendering time limit has been exceeded, or because you clicked the Stop Rendering button - and add more passes.
IRender nXt is a multi-pass rendering system. The early passes allow you to quickly check settings - such as lighting and materials. With Resume Rendering you can render for just 20 passes or os, see how it looks, and if you like it add more passes, or a time limit, and continue without having to start over.
After rendering, you can either make changes and restart the rendering, or use Resume Rendering to add more passes for better results.