VRayFresnel is a simple texture map that allows you to blend two colors or maps based on the angle of view and an index of refraction. For example you can connect the VRayFresnel texture to the specular color of a normal Maya material in order to create fresnel reflection.
Front Color - the color for the texture when viewed frontally.
Side Color - the color for the texture when viewed at a grazing angle.
IOR - index of refraction to use when calculating the Fresnel term.