The Japanese have three alphabets: two phonetic ones (hiragana and katakana, which both have 71 syllables) and kanji (the chinese characters).
Most japanese have english keyboards and they type in the word phonetically, the computer giving them options on which kanji combination could be used for that set of sounds. So let's say for the word Japan, you type in "nihon" (n, i, h, o, n) and the computer gives you a few options, the top one usually being the right one, 日本, so you just hit space (or select a different option with arrows and then hit enter). In fact, anyone can install it on their computer, so you can play around with it if you want.

You just need to add "Japanese" in Control_Panel/Regional_and_Language_Options/Languages/Details/Add. If "Japanese" is not an option, you need to install "Global IME (Japanese)", which you can find somewhere online. More info at http://www.msu.edu/~bellbri2/ime.html