Manyogana (万葉仮名 man'yōgana) was the "alphabet" of Chinese characters (hanzi) used in Classical Japanese to write Japanese phonetically. That is, a Chinese character was used only to represent a sound, without making use of the semantic value. Manyogana became obsolete in modern Japan, being supplanted by the systems of katakana and hiragana which derived from it—katakana characters consist of radicals or small components of manyogana, while hiragana are stylized cursive versions of the corresponding manyogana.
For example, the character 礼 became the katakana レ and the hiragana れ. One can easily see how this was done: For the katakana, the right half of the character was borrowed, while the hiragana is just the cursive style of the character.