This statement can be said to Jews on Friday before they celebrate the Sabbath on Saturday. It means peaceful sabbath in Hebrew.
SHALOM means peace and general greeting for all time to Jews. It is similar to Salam in Persian and Arabic.
Shabbath is the Saturday, the seventh day of the week for the Jewish calendar. A day off--free day beginning on Friday at sundown and ending on Saturday evening when the three stars appear in the sky and can be viewed together.
Shabbat recalls the Biblical Creation account in Genesis, describing God creating the Heavens and the Earth in six days, and resting on and sanctifying the seventh (Genesis 1:1-2:3). (thanks Wiki)
The supermarkets are packed with people buying their food for Saturday because in traditional homes, Jews have a huge feast with the family on Saturday but no cooking is done, it is prepared the night before. Prayers are said around the table as bread is broken.
Its a beautiful weekly holiday to relax and not check your emails, not use the phone and just relax and spend time with your family!