'Apple' is a count noun, and you can count it as one, two, etc.

Peroxides play an important role in chemical reactions.

A count noun, or 'kasu meishi', represents something that can be counted.

I somehow managed to pass the exam.

He said something or other to avoid being specific.

The wind direction has changed to east-southeast.

The wind is blowing from the east-southeast.

It is said that the story is heard throughout the village.

I failed to hear his name, could you tell me again?

I failed to hear his important remark.