What can Modern Orthodox Jews do on the Sabbath day?

Answer 1

Traditional Jews do not work on Shabbat (the sabbath). Orthodox Jews define work by the following 39 activities:

1 Planting

2 Plowing

3 Reaping

4 Binding sheaves

5 Threshing

6 Winnowing

7 Selecting

8 Grinding

9 Sifting

10 Kneading

11 Baking

12 Shearing wool

13 Washing wool (Scouring/Laundering)

14 Beating/Combing wool

15 Dyeing

16 Spinning

17 Weaving

18 Making two loops

19 Weaving at least two threads

20 Separating two threads

21 Tying

22 Untying

23 Sewing

24 Tearing for the purpose of sewing

25 Trapping

26 Slaughtering

27 Flaying

28 Curing hide

29 Scraping hide

30 Scoring

31 Cutting hide into pieces

32 Writing

33 Erasing

34 Building

35 Tearing something down

36 Extinguishing a fire

37 Igniting a fire

38 Applying the finishing touch

39 Transferring between domains

Answer 2

Not to do any of the prohibited forms of work

To say the day's prayers and hear the Torah-reading

To have the Sabbath meals

Answer 3

They pray at the synagogue and in the home.

Answer 4

Attend synagogue to pray and take naps.

Answer 5

Anything but a list of 39 prohibited acts. In the Talmud, tractate Shabbat, 12:1 it summarizes the spirit of the law as "one who does work on Shabbat and the work is enduring has violated shabbat." So, recreation, eating, worship, argument, all those are OK, but don't make things, plant things, harvest things, carry things (outside of your private domain), light fires, or put out fires (except to save a life). Saving someone's life on Shabbat is, of course, permitted even if it takes work.