Short answers, pulled from the story.
Katakana means "fragmentary kana." The name reflects how the characters were formed: each one was derived from a component or fragment of a more complex Chinese character, rather than from a full character as with other scripts.
The complete katakana script consists of 48 characters, organized into a 5-by-10 grid called the gojūon. Of those 48, only 46 are used in modern Japanese, and the vowel order in the grid was inherited from Sanskrit practice.
Katakana was developed in the 9th century during the early Heian period. It was created by Buddhist monks in Nara who needed a way to transliterate texts arriving from India and China into Japanese.
Katakana is used primarily to write foreign loanwords (gairaigo), country names, foreign place names, and foreign personal names. It also appears in technical and scientific terms, onomatopoeia, company names such as Suzuki (スズキ) and Toyota (トヨタ), and to indicate spoken accents or foreign-language dialogue in manga.
Hiragana is used for native Japanese words not covered by kanji and for grammatical inflections. Katakana functions more like italics in English: it marks foreign words, technical terms, emphasis, and onomatopoeia. Both are kana systems with one character per syllable, but they serve distinct roles in Japanese writing.
Katakana was added to the Unicode Standard in October 1991 with the release of version 1.0. The full-width katakana block is U+30A0 through U+30FF. Extensions for the Ainu language were added in March 2002 with version 3.2.