Honshu is the main island and the location of cities like Tokyo, Yokohama, Osaka and Kobe.
Hokkaido is Japan's second largest island. It is north of Honshu. That's where Sapporo is.
Kyushu and Shikoku are close to the south of Honshu.
Japan also has a chain of tropical islands to the south called the Ryukyu Islands. The biggest island here is called Okinawa.