It is customary to light at least two candles before Shabbat begins. One candle symbolizes remembering the Sabbath, as in Exodus 20:8, "remember the Sabbath day," and the other symbolizes observing the Sabbath, as in Deuteronomy 5:12, "observe the Sabbath day." These two verses appear in the two iterations of the Ten Commandments in the Torah.
Though there is no mention of lighting candles before Shabbat in the Torah, many texts from Torah help to explain the way that the ritual has evolved today. One of the prohibited categories of work on Shabbat was kindling a flame - for this reason, many chose to light a flame before Shabbat began. Over time, this practice evolved into kindling Shabbat candles. In a time before electric lights, this served a practical purpose; today Shabbat candles provide beauty and a celebratory atmosphere rather than serve any practical purpose.
Some families light more than two candles, adding a candle for each additional member of the family. Candle lighting is also customary before other holidays and festivals, like Rosh Hashanah, Yom Kippur, and Passover.
Whether you light Shabbat candles before sunset on a Friday evening, as part of a worship service at your local synagogue, or in your home with family or before a meal, this ritual can be a meaningful moment to reflect on the week that is ending, cultivate a sense of peace and gratitude, and think of loved ones near and far.