Some nouns are special, so we can't just add s to make them plural.
We need to add es to nouns that end with s, x, ch, or sh to make it plural.
Some students take the bus to school.
There are many buses that take students to school.
That box is heavy.
Those boxes are heavy.
We use a brush to paint.
We use many brushes to paint.
This tree has one branch.
This tree has many branches.