Green tea (Ryokucha) is ubiquitous in Japan and therefore is more commonly known simply as "tea" (ocha). It is even referred to as "Japanese tea" (nihoncha?) though it was first used in China during the Song Dynasty, and brought to Japan by Myōan Eisai, a Japanese Buddhist priest who also introduced the Rinzai school of Zen Buddhism.
Types of tea are commonly graded depending on the quality and the parts of the plant used as well as how they are processed. There are large variations in both price and quality within these broad categories, and there are many specialty green teas that fall outside this spectrum.