Question

Answer

"Work" technically means performing one of the forbidden areas of activity, known in Hebrew as "melakha" or creative activity.

If on Shabbat you carry a feather outside the private area into the public, you've "worked" but if you move a piano from the first floor to the second floor you have not "worked." Thus, it is not work as we understand it in English and use it most often.

Look up "work" and "Shabbat" in the Encyclopedia Judaica and you'll get a fuller explanation.