3 Tier architecture is structural pattern of an application , where 3 layer works separately like Business layer , Presentation layer and Data layer
3-Tier Architecture means aUser Interface Layer - For interaction(GUI Forms)Business Interface Layer - to handle the business logic (Calculation part ) -BIData Interface Layer -- To handle the Data i.e., From Database Connections, Calling StoredProcedures, - DIInfo Layer -- To handle the Get,Set Properties mostly common Mostly BI & DI are the class libraries build into the projects or components if used in multiple projectsThe main purporse is to maintain the Code in an understable format for developers worldwide, easy maintainance.