Have a look at the online help topic for With...Endwith. it explains it fully. An example of use might be:

Instead of:

thisform.pgfMain.pagEmployees.text1.enabled=.f.
thisform.pgfMain.pagEmployees.text2.enabled=.t.
thisform.pgfMain.pagEmployees.text3.enabled=.f.

You can do this:

WITH thisform.pgfMain.pagEmployees
.text1.enabled=.f. && Now I don't need the whole object refrerence
.text2.enabled=.t.
.text3.enabled=.f.
ENDWITH

It's just a shortcut in typing out code.