Challah is the traditional plaited bread especially baked for Friday night and Saturday daytime (Shabbat) and other holidays.
Two challot (the plural of challah) are used for both Shabbat meals (Friday night and Shabbat Day). This commemorates the double portion of manna that the people of Israel in the desert received from G-d before Shabbat. This also reminds us of the two biblical commandments of Remembrance (Zachor) and Guarding (Shamor) the Shabbat and its sanctity.
The meal continues with Challah blessing: