A type of noun which can be counted, like computer (one computer, two computers, three computers, etc.). In contrast, there are non-count nouns like software which can't be counted.
In terms of meaning, nouns are sometimes described as ‘naming words’ – words for people, animals and things. The noun class does include many words of this kind: brother, baby, rabbit, horse, handbag, chair. These all refer to physical beings or objects – they are concrete nouns. But there are also many abstract nouns – nouns with abstract (non-material) meanings, like pleasure, sight, kindness.