It is a Japanese syllabary alphabet used to spell out foreign, now mostly English words. Consists of approx. 45 syllables, which can be further modified with accents "=b and °=p, prolongations (nigori) and smaller versions of vowels, ya-yu-yo and tsu. It doesn't allow for an exact transliteration, thus introducing a thick Japanese accent.

katakana "カタカナ" is one of the three Japanese writing systems; including Hiragana, and Kanji. katakana is mostly used for foreign words (usually English.) So Car becomes
"クルマ"(kuruma) and burger becomes "バーガー"(baagaa)

the full Katakana Alphabet:

a i u e o
アイウエオ
カキクケコK
サシスセソS
タチツテトT
ナニヌネノN
マミムメモM
ハヒフヘホH
ヤ ユ ヨY
ラリルレロR
ワ ヲW

ン n
ダヂヅデドD
ザジズゼゾZ
バビブベボB
パピプペポP