Can you count your friends, the chairs around your kitchen table, your books and the apples in your fridge? I think so. However I am sure you cannot count the milk you had for breakfast this morning nor the bread you made your sandwich with.
COUNTABLE NOUNS UNCOUNTABLE NOUNS
for example: There is an apple on the table. There are two apples on the table.
When a noun is UNCOUNTABLE there is only the singular form
for example: There is some pasta in the plate.
You CANNOT use A/AN with UNCOUNTABLE nouns but you MUST use SOME.
SOME can also be used with COUNTABLE NOUNS when they are plural (always in positive sentences).
for examples: There are some apples on the table.