Business logic

Business logic is a non-technical term generally used to describe the functional algorithms which handle information exchange between a database and a user interface. There exists no definition of business logic in any programming language specification or API, nor in any academic research. However, usage of the term persists in trade publications where several individuals have tried to informally advance a meaning that could be standardised. The term can be applied to web application development where programs are separated into a 3-tier architecture with business logic referring to the mid-tier. It should be noted that business logic is a poorly-defined term which is used in several different ways by several different groups of people.

Reference:
http://en.wikipedia.org/wiki/Business_logic