What does the candles on the seder table represent?

The two Shabbos (Sabbath) candles represent Zachor (Exodus ch. 20, remember the shabbos) and Shamor (Deuteronomy ch. 5, keep the shabbos). All of the Yamim Tovim (festivals), Pessach (Passover) included, are also termed "shabbos" and share in many of the shabbos laws and observances, including lighting two candles shortly before the holy day begins.