What are countable nouns? What are some examples of countable nouns?
A countable noun is a noun which can be used with numbers. See explanation.
A noun is countable if it can be used with numbers and has plural form. For example a dog is acountable noun because you can say for example "five dogs"
An uncountable noun is a noun that has no plural form and cannot be used with numbers (without additional words).
For example salt is uncountable, because you cannot say anything like three salts. If you want to count such nouns you have to use additional "unit" words like (a soon, a kilogram etc.). You cannot count salt, but you can write for example three spoons of salt, ten kilograms of salt etc.