Page break be­fore forces a para­graph to start at the top of a new page. Vi­su­ally, there’s no dif­fer­ence be­tween us­ing the page-break-be­fore op­tion and typ­ing a hard page break in front of the para­graph. But that’s only ef­fi­cient for the oc­ca­sional paragraph.

The page-break-be­fore op­tion is in­tended to be in­cor­po­rated into para­graph and char­ac­ter styles so all para­graphs of a par­tic­u­lar style will start at the top of a new page. For in­stance, you might ap­ply it to your top-level head­ing style. In a long doc­u­ment, typ­ing hard page breaks in front of each head­ing would be tedious.