"Business Requirement" is a jargon term used in software and product development processes. The term requirements is prefixed with "Business" to differentiate them from other types of requirements such as system requirements or functional requirements.
Essentially a business requirement is something a business percives it requires. This requirement if often created in the context of a software or process improvement but may also be used in the context of other product development activities.
The purpose of having a 'business' requirement is to ensure the requirement is abstracted away from a particular solution technology. People refer to teh concept of "business requirements are solution agnostic."