Shabbat candles are traditionally lit by the woman of the household, and most people will light two to symbolize the commandments of both remembering and keeping the sabbath. Some families even light additional smaller candles, one for each child they have.

Lighting the candles is considered an important mitzvah and often times a woman will wave her hands over the flame (after lighting) signaling that she is welcoming in Shabbat. The eyes are then covered while the below blessing is recited.

 
Barukh atah Adonai, Eloheinu, melekh ha'olam
Blessed are you, Lord, our God, sovereign of the universe

asher kidishanu b'mitz'votav v'tzivanu
Who has sanctified us with His commandments and commanded us

l'had'lik neir shel Shabbat. (Amein)
to light the lights of Shabbat. (Amen)