It must be bought abroad and stamped in Japan before you can use it. There are several options including one week (unlimited JR travel except for the super fast Nozomi service), two week, JR East and JR West passes. Check with your local travel agent for the best option or click on the link to see for yourself!
Here is a link to a very cool page that lets you see the routing between cities/stations/ports within Japan. It will tell you the route and includes the cost and time. http://www.jorudan.co.jp/english/norikae/.
I have also found this website which is extremely useful, in English with details of timetables all over Japan.
http://japanrail.com/index.html


