What are event keywords in reports? | SAP-ABAP

 Following are the event keywords in reports:
?    INITIALIZATION
?    AT SELECTION-SCREEN
?    AT SELECTION-SCREEN ON <field>
?    START-OF-SELECTION
?    TOP-OF-PAGE
?    TOP-OF-PAGE DURING LINE SELECTION
?    END-OF-PAGE
?    END-OF-SELECTION
?    AT USER-COMMAND
?    AT LINE-SELECTION
?    AT PF<NN>
?    GET
?    GET LATE
?    AT User Command.