The Infotype Concept within Personnel Administration 
Infotypes are used in Personnel Administration and Recruitment. An infotype is a group of object-based pieces of information on a particular area. The data stored in an infotype is always based on the personnel number of an employee or the applicant number of an applicant. In other words, an infotype record is always assigned to exactly one employee or applicant.
A four digit number
nnnn is assigned to each infotype. This number uniquely identifies an infotype. The number range 9000 to 9999 is reserved for customer infotypes.Transaction PM01 Enhance Infotypes enables you to create and edit infotypes.
See also:
Definition of an Infotype within the Data Dictionary Module Pool for an Infotype Screens for an Infotype Dialog Module for an Infotype Characteristics of an Infotype Infotype Text Modules