The GetWindowText function will copy the text of the specified window's 
title bar into a buffer. If the specified handle is a control, the text 
or caption of the control is copied to the buffer. 

function GetWindowText(hWnd: HWND; lpString: PChar; nMaxCount: Integer): integer;

Quick Copy&Paste:
-----------------
 
 GetWindowText(Handle, lpString, Integer);
 GetWindowText( , , );

Commented:
----------

  GetWindowText(
    hWnd: HWND;         //handle of window or control with text
    lpString: PChar;    //address of buffer for text
    nMaxCount: Integer; //maximum number of characters to copy
   ):integer;	

User Contributed Examples:
--------------------------

 Example #1:
 
  var
   lpString1: pchar;
  begin
   GetWindowText(Self.Handle, lpString1, 50);
   showmessage(lpString1);
  end;

 Example 2:

 Example 3:

User Contributed Comments:
--------------------------
 Comment #1...
  In Example #1 lpString1 is a pchar (like a string) parameter 
  that the procedure receives after sending the API message.
  Once you send the GetWindowText message, the lpstring1 then
  retrieves what it needs and you have access to it.

 Comment #2...