From Lazarus-ccr

The end keyword closes a block of instructions started with the begin or case keyword, ends the declaration of fields of a record, or closes a try .. finally or try .. except construct. It is also used to close a unit having no initialization code.

For example:

 
  procedure Proc1;
 
  var a,b: integer;
 
  begin
    (..)
  end;
 

It is also used to end a pascal source file, in which case it is followed by a period rather than a semicolon (in the example below, the last semicolon is optional):

 
  program Proc2;
  var
    SL: TStrings;
  begin
    SL := TStringlist.Create;
    try
      (..)
    finally
      SL.Free;
    end;
  end.
 

For a UNIT which contains no initialization, END is used to indicate the end of the unit:

 
  unit detent;
  uses math;
 
  procedure delta(r:real);
 
  implementation
 
  procedure delta;
  begin
 
  ...
 
  end;
 
  ...
 
 (* Note: No '''begin''' statement *)
 
  end.
 

Keywords: begin — do — else — end — for — if — repeat — then — until — while