Functional Specification

Functional spec is nothing but a Business requirement document , it is just an approved artifact which you draft in a way which will be clear for a technical person to use it further for their development. every module has their own functional spec's drafted . It is required at the time of development. Userexits are subprograms which were linked to the standard SAP to fulfill the requirements of the client. These userexits can be used at the order level, delivery level as well as invoice level also.