Dell Latitude E6410 button "Latitude ON"? --What does button do?

Small button next to the power on button.  Exactly how does the button function?  Not asking about "Latitude ON" itself, but the purpose of the button (Enable/Disable?).

I spent 45 minutes on phone with the little Indian snots because CHAT window function will not open without your "SERVICE TAG" or the "EXPRESS SERVICE CODE" on the bottom of the laptop (or any other Dell product). And you cannot get any customer service from a person on the phone without that either. So I gave them one of my many Dell service tags (from a Dell printer or a Dell monitor or a Dell Dimension desktop or a Dell Inspiron laptop or my 1998 Dell Latitude laptop). Of course, they refused to believe in that last service code--not enough digits. 
Anyway, no one at Dell support would tell me anything about the button on an E6410 because I am not the  owner and I don't have the service tag or express service code to give them. And after a long time on hold (as the little girl requested I do), my phone got cut off. 
I guess tomorrow I will have to call Dell executive offices in Round Rock Texas and ask why there is no documentation on line or in user manual about that mystery button and what it does. Plenty of pages of "Latitude ON" purpose, but nothing about the button with the same symbol.

See Yahoo Answers question about this at: answers.yahoo.com/.../index;ap=4&ans_success=1