The name Kwanzaa is derived from the phrase “matunda ya kwanza” which means “first fruits” in Swahili. Each family celebrates Kwanzaa in its own way, but celebrations often include songs and dances, African drums, storytelling, poetry reading, and a large traditional meal. On each of the seven nights, families gathers and a child lights one of the candles on the Kinara (candleholder), then one of the seven principles is discussed.
The principles, called the Nguzo Saba (seven principles in Swahili) are values of African culture which contribute to building and reinforcing community among African-Americans. Kwanzaa also has seven basic symbols which represent values and concepts reflective of African culture.
The candle-lighting ceremony each evening provides the opportunity to gather and discuss the meaning of Kwanzaa. The first night, the black candle in the center is lit (and the principle of umoja/unity is discussed). One candle is lit each evening and the appropriate principle is discussed.
Source: https://www.history.com/topics/holidays/kwanzaa-history