White soy sauce is produced with more wheat than soybeans and it contains 50% less "umami" than regular color soy sauce (Koikuchi), as regular soy sauce is typically made from equal amounts of soybeans and wheat.
Mainly used for:
White soy sauce is originally made in Aichi prefecture. And from its amber color, it is mainly used at sophisticated traditional Japanese restaurants for not adding too much color of soy sauce to the cuisine and highlight original color of ingredients (e.g. carrot's red, green beans).