Verb Groups

In Japanese, verbs are sometimes divided into group 1, group 2, and group 3, or type 1, type 2, type 3, or class 1, class 2, class 3, ichi-guruupu Iグループ, ni-guruupu IIグループ, san-guruupu IIIグループ, or whatever in the world your teacher, book, resource, material, or blog is calling it now.

Point is: there are three groups of verbs in modern, standard Japanese, which group verbs according to their conjugation, and for some reason are always, consistently enumerated in the following order:

1. godan verbs, also called consonant-stem verbs,
2. ichidan verbs, also called vowel-stem verbs, which always end in ~eru or ~iru.
3. The rest. Which are only two verbs: suru する and kuru 来る, which are also called irregular verbs.

As long as you aren't reading some poem from the 9th century, any verb you find in Japanese will fall into one of the three groups above. In other words, if you know how to conjugate the three groups, you know how to conjugate any verb in Japanese.

See also: ichidan vs. godan verbs.