What do you mean by "type of Japanese"? If you're referring to spoken Japanese, the Tokyo dialect is the standard dialect, though there is still some regional variability.
If you're referring to written Japanese, the three writing systems are used together. Kanji (Chinese characters) are used for verbal and adjectival stems, and many nouns. Hiragana is used for grammatical elements and most Japanese origin nouns, and katakana is used for foreign borrowed words and onomatopoeia.
If you're referring to style, (ie whether you use masu/desu or ru/da endings) then both are used, which one is used most depends on which kind of people you spend the majority of your time talking to. If you're talking to people older than you or people in a business context most then you use masu/desu, if you're mostly talking family and friends then ru/da.