Thank you for your question about the Buddhist altar. Let me outline those things that comprise the Nichiren Buddhist altar:
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 fundamental substance) to the Buddha (Gohonzon). Water also signifies the pure life cleansing attribute of the Buddhist Law. 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 tasting of the True Teachings and the sense of taste.
5). A candle holder and candle for offering the Light of the Dharma (teachings) to the Buddha. The candle also signifies lighting the way for all sentient beings and 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 and the sense of hearing
7). An incense burner and incense to offer beautiful aromas to the Buddha, to purify the air for the Buddha, and it symbolizes the sense of smell.
8). A vase for offering fresh flowers or evergreens to the Buddha.