Thank you for your question about the Buddhist altar. Let me first outline those things that comprise the altar of our sect:
1). The Object of Worship which is The Master of Teachings Lord Shakya of the 16th Chapter of the Lotus Sutra at the moment of transmission of Namu Myoho renge kyo or the Gohonzon. The Gohonzon may be housed in a cabinet called a butsudan or, if in a protected environment, attached directly to the wall.
2). An altar table
3). A water cup for offering water(the most fundemental substance) to the Buddha. The water is drunk and changed daily. The cup is left covered on the altar.
4). A Bowl of fresh fruit or other slowly perishable food which too is an offering to the Buddha. It signifies the sense of taste. It also signifies the tasting of the True Teachings.
5). A candle holder and candle for offering the Light of the Dharma (teachings) to the Buddha. The candle also signifies giving light to all sentient beings. It also signifies the sense of vision.
6). A bell and striker for offering music to the Buddha. The bell also signifies spreading the True Teachings with one's voice. It also signifies the sense of hearing
7). An incense burner to offer beautiful aromas to the Buddha. It is also to purify the air for the Buddha. It also symbolizes the sense of smell.
8). A vase for offering fresh flowers or evergreens to the Buddha.