I've written this query with the help of google to create a delimited list from a table but I didn't understand anything from this query.

Can anyone explain me what's happening

 SELECT 
    E1.deptno, 
    allemp = Replace ((SELECT E2.ename AS 'data()' 
                       FROM emp AS e2 
                       WHERE e1.deptno = e2.DEPTNO 
                       FOR xml PATH('')), ' ', ', ') 
 FROM EMP AS e1 
 GROUP BY DEPTNO; 

Gives me result

10  CLARK, KING, MILLER
20  SMITH, JONES, SCOTT, ADAMS, FORD
30  ALLEN, WARD, MARTIN, BLAKE, TURNER, JAMES