"Kuro" is the Japanese word for black.
Raku ware is not made by a potter's wheel but is shaped by hand, and uses a special firing process that results in unique and somewhat thick shapes.
This Matcha bowl is baked without a glaze and after the baking is glazed many times. After each baking, it's baked again at high heat then cooled; a rather intense and time consuming process. The glaze turns black due to the rapid cooling.
Since it is hand made, the shapes and designs will vary from the picture.
Pottery: Kyoyaki pottery has been produced since the middle of 17th century and many famous artists were born with Kyoyaki.