Vouchers,Rebate Codes,Promo Codes,Promotional Codes or Markdown Codes.What ever you want call it its phenomenon of the Modern Society we are living.
Here one long story to read about called
5 Short Answers for Consumer Society Applying Discount Codes
Here link full story
Hope you will all read it and will give your feedback about it.
Personally is well written and quite understandable which I might call the Headline as 5 Principle in Consumer Society when it comes about Discount Code and other variation semantic ones following the word Discount Codes.
Redacted and Edited from J.K Rowling