What are classes?

When you file a trademark application in Japan, you must indicate the goods and services that you are using your trademark with (or that you plan to use your trademark with). All goods and services are classified into 45 different categories, called International Classes. These were defined by a treaty called the Nice Classification System (after Nice, France). The JPO provides a guide of acceptable wording and corresponding classes. If the specific items you want to include in your trademark registration are not listed there, it can be helpful to discuss your application with an experienced attorney.
See https://www2.j-platpat.inpit.go.jp/SH1/sh1e_search.cgi?TYPE=000&sTime=1458524681254.