Events in ABAP are
initialization
at selection-screen
start-of-selection
get
end-of-selection
at line-selection
at pfn
at user-command
top-of-page
end-of-page

There are several events
In Clasical Reports
1.Initialization
2.At Selection-Screen.
3.Start-Of-Selection.
4.Top-of-page.
5.End-of-page.
6.End-of-selection.
In Interactive Reports
1.At Line-Selection.
2.At PF key
3.At User-Command
4.Top-of-page During Line-Selection.

These are the following events in Sap ABap..
 * load-of-porgram
 * initialisiion
 * at screen selection
 * strat-fo-selection
 * top-of-page
 * end-of-page
 * end-of-selection
 * top-of-page during line selection
 *at line-selection
 * At new
 * at end of
 * at last
 * At first
 * At user-command
 * At pf and so on

THERE ARE MAINLY 11 ELVENTS USED IN ABAP. THESE ARE
1>  TOP-OF-PAGE
2>  END-OF-PAGE
3>  AT LINE-SELECTION
4>  AT USER-COMMAND
5>  AT PFn
6>  GET
7>  START-OF-SELCTION
8>  END-OF-SELECTION
9>  AT SELECTION-SCREEN
10> AT NEW
11> INITIALIZATION.

USING OF EVENTS DEPENDS UPON REPORT. 
AS IN CASE OF INTERACTIVE REPORT WE USED:
1>  AT LINE-SELECTION
2>  AT USER-COMMAND
3>  TOP-OF-PAGE
4>  END-OF-PAGE

IN CASE OF CLASSICAL WE USED:
1>  Initialization
2>  At Selection-Screen.
3>  Start-Of-Selection.
4>  Top-of-page.
5>  End-of-page.
6>  End-of-selection.

In Clasical Reports
--------------------
1.Initialization
2.At Selection-Screen.
3.Start-Of-Selection.
4.Top-of-page.
5.End-of-page.
6.End-of-selection.

In Interactive Reports
----------------------
1.At Line-Selection.
2.At PF key
3.At User-Command
4.Top-of-page During Line-Selection.
5.GET
6.GET LATE