All the visas (status of residence), except for Permanent Resident visa, have a fixed period of stay and need therefore to be extended if you wish to stay in Japan longer.
The application for the Japanese Visa renewal is to be submitted at the nearest Immigration Office in your city. There is no limit for the number of extensions that can be granted (except for some types of visa such as Trainee and Cultural Activities), as long as you meet all the requirements.
Once the application for the visa renewal is submitted, your current visa is automatically extended for 2 months, during which time the application is processed and the result is notified.
It is possible to travel outside of Japan while the application for the visa renewal is being processed as long as you will come back to Japan before the end of this 2 months' extension. In the case your application is rejected, a new temporary status will be given, which will allow you to prepare for the departure. If you return to Japan 2 months after the visa expiration date, your visa will be cancelled even if the renewal application is in process.