How many candles are lit at minimum? And what do they represent?

At minimum, two candles are lit for Shabbat, corresponding to the two versions of the Shabbat commandment: 'Zachor' (Remember — Exodus 20:8) and 'Shamor' (Keep/Guard — Deuteronomy 5:12). These two words were miraculously pronounced simultaneously at Sinai. Many women add a candle for each child, so a mother of three might light five candles. The two candles also symbolize the duality of Shabbat: the active remembrance through Kiddush and songs, and the guarding through abstaining from work.