Shabbat (the Sabbath), the Jewish holy day of the week, starts at sunset on Friday and ends shortly after sundown on Saturday evening. All public offices, banks and many stores are closed on Shabbat. Museums, national parks and most art galleries are open. Restaurants (not supervised kosher) and entertainment spots are open. On Shabbat, buses and trains do not run in every city, but taxis do. Airports are open as well.
Naturally, cities differ from each other. For example, while Tel Aviv is mostly open on Shabbat, Jerusalem will mostly be closed. But there is still lots to do around the country, even on Shabbat. Just ask us for some recommendations!