Katakana (カタカナ) is one of the two sets of syllable writing used in Japanese. Katakana is usually used for foreign terms, foreign names and most of Go technical terms.
Today's Japanese is written in a mixture of three writing systems, two of them syllable sets, hiragana (the squiggly letters), katakana (the edgy ones) and kanji (the small pictures with the many strokes).
When looking at a Japanese word, the kanji can give a hint about the original meaning or the concepts involved in the expression. Some go terms are written in katakana.
Examples of words in katakana: ピアノ バナナ テニス ゴルフ コーヒー ビール