J-pop is short for Japanese pop, which is of course from Japan. Although many K-pop artists, sing and perform songs in Japanese. J-pop subgenres can include j-rock (Japanese rock) and j-hip hop (Japanese hip hop).
Popular Japanese j-pop artists like AKB48, Ayumi Hamasaki, E-girls, EXILE, FLOW, Hey! Say! JUMP, NEWS, SCANDAL, Kyary Pamyu Pamyu, and KAT-TUN are well known in Japan, Asia, and the Western countries.
K-pop groups like Girls’ Generation, SHINee, Super Junior, GOT7, 2NE1, and many others sing in Japanese.