Is Shabbat Jewish

Answer 1

Yes, Shabbat is the Jewish weekly day of rest.

The Jewish Sabbath is from Friday sundown until Saturday after twilight. The origin of the Shabbat is in the Torah (Genesis ch.2, Leviticus ch.23, Exodus ch.20 and many other passages). Since the Sabbath is a day blessed by God (Genesis ch.2), he gave it to the Israelites as a treasured gift to be cherished (Talmud, Beitzah 15b). It is a day of rest (Exodus ch.20, ch.31), and a day of strengthening ties with the family, the community, and with God.
There are two main aspects to Shabbat observance: what we do and what we don't do.
What we don't do: we're not permitted to work on the Shabbat (Exodus ch.20). This includes 39 categories of productive interaction with the world, such as planting, writing, kindling fire, etc. (Talmud, Shabbat 73b).

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What we do: candles are lit, customarily by the lady of the household, around 20 minutes before sunset on Friday afternoon. We then attend synagogue for the Friday afternoon prayer (mincha), the kabbalat Shabbat (ushering in of the Shabbat), and the Shabbat evening prayer (maariv), consecutively.
On Shabbat morning, we again attend synagogue. The services are longer than on weekdays and include prayers as well as reading the weekly Torah-portion.
There's often a kiddush (refreshments) afterwards, and congregants then have a chance to schmooze (to talk). Towards the late afternoon, there's another (short) service (Shabbat mincha).

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After Friday night services and on Shabbat morning after services, we come home, often with guests, make kiddush (blessing over wine), and have a leisurely multi-course Shabbat meal including singing and words of Torah. Customarily, that week's Torah-reading (parsha) will be a topic of conversation; and the children of the family will be asked to speak of what they've learned in school.

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After that, Shabbat is a quiet time: no phones, radio or TV (etc.), just schmoozing, taking walks, visiting friends, reading, learning Torah, playing Board Games, etc.
Husband and wife, in particular, finally have a chance to be together after a hectic week.