1. What is it about the Sabbath that Jews take so seriously?  I have Jewish neighbors who don't compromise an inch on its observance.  I admire their devotion and I wonder if you could give me more understanding.

The answer to your question is founded in this text from the Torah.  Hashem said

to the children of Israel at Mt. Sinai:

You shall keep the sabbath, for it is holy for you. He who profanes it shall be put to death: whoever does work on it, that person shall be cut off from among his kin.  Six days may work be done, but on the seventh day there shall be a sabbath of complete rest, holy to the L-rd; whoever does work on the sabbath day shall be put to death. The children of Israel shall keep the sabbath, observing the sabbath throughout the ages as a covenant for all time:  it shall be a sign for all time between Me and the people of Israel. For in six days the L-rd made heaven and earth, and on the seventh day He ceased from work and was refreshed.  Exodus 31:14-17

The Sabbath (Shabbat in Hebrew) is, in Hashem's own words, a 'sign for all time'of the covenant He made with the children of Israel.  Therefore it is of the utmost importance to Jewish people and rightly so.  Once every week, we dedicate an entire day to remembering Who called us to be His people and how we are to live to fulfill that calling.  Shabbat is the highlight of the Jew's week.

It may be interesting to you to note that the Sabbath is the first thing in the bible to be called 'holy'.  The commandment to rest is in keeping with the context of the commandment.  We are to rest from 'creative' work, as Hashem rested from His creating.  Therefore, observant Jews do not paint, sculpt, write, or do anything of a creative nature on Shabbat.  There are other activities that we forego on Shabbat in honor of Hashem and His covenant with us. For more information about Shabbat,

I recommend that you visit this website: http://www.aish.com/shabbat/ which provides an abundance of information, teaching and inspiration regarding the observance of Shabbat. 

2. When did the tradition of lighting candles on Shabbat begin and why?

The Torah does not specifically command the lighting of candles but it is a custom that was developed and promulgated by rabbinic authority to promote the holiness of Shabbat.  It is written in the Mishnah and the oldest record of candles being lit with a blessing goes back to the 8th century. The lighting of the two candles is accompanied by the well-known blessing which concludes, "l'hadlik ner shel Shabbat," "Praised are You, O Lord.who has commanded us to light the light of Shabbat." The traditional explanation is that the two candles are lit based on the two times the Torah commands us to observe the Sabbath. Once we are told to "shamor," to watch over the Sabbath day; and once we are told to "zakhor," to remember the Sabbath day. Each candle serves as reminder of God's two commandments.

There is something very special about the act of lighting Shabbat candles. One of the strongest symbols of the Jewish people, candle lighting encompasses what is central in Judaism: the Jewish home.  It is a moment steeped in tradition, as one may remember one's own mother lighting... or one's grandmother... or the Jewish women who have been lighting candles every Friday night for 4,000 years. It is a powerful link to Jews everywhere; one that, until recently, remained unbroken in every home, in every land.

Customs vary, but in a family there are always at least two candles burning: one for the wife, and one for the husband, a symbol of Shalom Bayit (peace in the house). Many add one candle for each child, as each is an additional blessing, each a source of new light coming into the world.

Lighting the Shabbat candles is one of the special mitzvot for women. Why is this important mitzvah assigned to women? Because it is light, and that is the essence of a woman.  It is the woman who brings light into the home, providing the atmosphere in which she, her husband, and her children can live and prosper. The tone, the feel, the look is from her. When she is happy and positive, even the most depressed husband or tired child will absorb her energy and be lifted.  However, if she is unhappy and the home has a feeling of negativity, it can affect the whole family. She is the core of the family unit. It is the power of the Jewish woman.  Historically, it was the Jewish women, not the men, who agreed to accept the Torah first at Mount Sinai. Today, it is the woman who transmits the essence of our Jewish heritage into every home.

So this is how the Shabbat begins, with special light; special understanding as to why we are and why we are here. For Shabbat is our time to connect with God; when we stop creating in order to recognize that there is a Creator. The entire week we are caught up in a hectic pace, where it is easy to think only of personal accomplishments and individual achievements.  But, once the candles are lit, it is time for love of God; for remembering that everything is from Him. It takes but a few seconds to do, but it is by far one of the deepest expressions of the Jewish soul: to recognize the Almighty and appreciate this special gift that He has given to us all -- a gift we call Shabbat.

Zachor and Shamor: Remember and observe. Two distinct concepts, when fused together, represent the full understanding of the Sabbath. To observe is to keep the law, without which there is no Sabbath day. To remember, denotes a longing for the Sabbath, which is why it is a custom to view each day of the week as a prelude to the coming Shabbat, and an almost unwillingness to let go of the previous Sabbath.