The Shabbat:

Bottom-line, the Shabbat is the holiest of all days.  "Remember the Day, the Shabbat, to set it apart for G-d." Exodus 20:4.  The Seventh Day/Shabbat begins Friday evening, or Erev Shabbat, and concludes Saturday just after sundown.  Often times we conclude the Shabbat with Havdalah, which makes a distinction between the Shabbat and the other days of the week.  In concluding the Shabbat with the Havdalah service, we look forward to the rest of the week and especially towards the next Shabbat.