Kana (the term is both singular and plural) are Japanese phonetic characters. They come in two types: hiragana and katakana. Cf. Japanese language. The term is derivered from katakana, hiragana.
As well as Romaji Kana is quite frequently used for transiliteration, a method to express one language in the alphabet of another language. Given that, kana is regared as alphabet in Japanese. For example, the United States President George W. Bush can be represented in Japanese using kana like ジョージ ブッシュ (Note: in Japanese convension, the middle name is generally omitted.)
See also: Hiragana, Katakana, Romaji, Transiliteration