Hello Ram,
SM13 is used to verify pending update requests. You can delete update requests you do not want anymore (check with functional area first!) or reprocess requests that failed. Read the following SAP Help page for more details:
Update Management - Updates in the SAP System (BC-CST-UP) - SAP Library
SM14 is used to administer the update mechanism itself (e.g., activate/deactivate the update mechanism, manage update groups, ...).
Regards,
Isaías
