Hi,
Please find the links below which are self explaining.
IT 2001 - Absences used for any deviations which leads an employee absence
IT 2002 - Attendances used for any deviations which leads an employee absence from office but Authorized by Company or any process and etc.
List of HR Infotypes | Uday's website
http://www.saphrfunctional.org/sap-hr-infotypes
C.Praveen