There are two cases: Illuminance (usually 'E' in formulas) is the total amount of visible light illuminating (incident upon) a point on a surface from all directions above the surface. This surface can be a physical surface or an imaginary plane. Therefore illuminance is equivalent to irradiance weighted with the response curve of the human eye. Standard unit for illuminance is Lux (lx) which is lumens per square meter (lm/m 2).
http://www.schorsch.com/en/kbase/glossary/illuminance.html
1 Reflect light-if it has a. 2  e.g. mirror surface. 3  Refract light-if it is transparent to the wavelength of light that reaches its surface (e.g. if it consists of colourless glass and is illuminated by visible light e.g. a green laser beam) and the light reaches the surface of the object within a certain range of angles.
http://www.ivyroses.com/HumanBody/Eye/Light-on-objects.php
We use the same word light for electromagnetic radiation of frequencies in the narrow band 4 x 10 14 Hz to 8 x 10 14 Hz, and also for the psychological sensation produced by it when it impinges on our eyes and excites our visual sense. The energy in physical light can be expressed in watt, which is precisely defined.
http://mysite.du.edu/~jcalvert/optics/lumens.htm
Incoming light interacts with a surface and may be absorbed, refelected, and/or transmitted. Materials have a reflectance spectrum which is a function of the angle of incidence of the incoming light. The color of an object is a function of the color spectrum of the incident light and the reflectance spectrum of the object surface. For example, if an object absorbed all the light except for red then the object would appear to be red in a white light. So the reflectance spectrum of a red object would look like this:
http://www.siggraph.org/education/materials/HyperGraph/illumin/reflect1.htm
The illuminance or light level is the amount of light energy reaching a given point on a defined surface area, namely the luminous flux (i.e. lumens) per square meter. Illuminance is invisible!
http://www.dnp-screens.com/DNP08/Technology/Basic-Visual/What-is-light/Illuminance.aspx
Luminous emittance is a deprecated term for Luminous Exitance. (Terms of photometry). Luminous flux density is photometrically weighted radiant flux density, which means luminous flux per unit area at a point on a surface where the surface can be real or imaginary.
http://www.schorsch.com/en/kbase/glossary/illuminance.html
The reflectance spectrum is frequently a function of the incident angle. For example, here is how the reflectance spectrum of copper changes with the angle of incidence. Image Reference. The reflected spectrum is the incoming light spectrum times the reflectance spectrum of the surface. For example the above red object illuminated with perfect white light would appear red: A more complex example is copper.
http://www.siggraph.org/education/materials/HyperGraph/illumin/reflect1.htm
Absorption. Light energy. . Because the light goes. the object rather than leaving the surface of the object-and then some of that light entering the eye-the object is not  seen  as very bright. Instead, it is perceived to be dark (meaning that little light is traveling from that object into the eye).
http://www.ivyroses.com/HumanBody/Eye/Light-on-objects.php
Illuminance is measured in lux and the measurement will include all light reaching the point of measurement from a 180 o hemisphere. Lux levels relevant to the perception of light range from below 0.1 lux to above 120,000 lux. The lux value is used to describe the amount of light in a given environment. A living room may have an illuminance level of 100 lux, an office 500 lux and direct sunlight greater than 120,000 lux.
http://www.dnp-screens.com/DNP08/Technology/Basic-Visual/What-is-light/Illuminance.aspx
Reflection vs. Scattering : When light is reflected at a surface, it leaves that surface in a. (according to the Law of Reflection). When light is scattered at a surface, it leaves that surface in. . An example of a reflecting surface is a high-quality mirror.
http://www.ivyroses.com/HumanBody/Eye/Light-on-objects.php
what is the term for the light that illuminates a surface?
Illuminance is the term for the light that illuminates a surface. The term for the light that illuminates a surface is illuminance.