Nouns can be either countable or uncountable. Countable nouns can be counted and have both a singular and plural form, while uncountable nouns only have a singular form and cannot be counted. Different determiners and quantifiers are used with countable and uncountable nouns, such as "some" and "any" can be used with both, while "many" and "few" are only used with plural countable nouns and "much" and "little" only with uncountable nouns.