It is a tricky topic because some uncountable nouns (e.g. information) in English have their equivalents in other languages that are countable. In some cases, a noun is uncountable (e.g. experience) but we can put an indefinite article in front of it making it countable (e.g. an experience). Here we refer to an event. The best way to learn these differences is to consult a good dictionary and practice a lot.
Concrete and abstract nouns
Many countable nouns are concrete:
Persons: A boy, a girl, a woman, a man
Animals: A cat, a bird, a snail
Plants: A rose, a pine, a cactus
Objects: A pen, a card, an iron
Groups: A crowd, a bunch, a herd
Units of measurement: A milligram, a kilo, a gallon
Parts of a mass: A piece, a fragment, a shard
Concrete uncountable nouns
Concrete uncountable nouns include:
Materials: silk, cotton, metal
Liquids: water, oil, wine
Gases: helium, oxygen, hydrogen
Grains/powder: barley, buckwheat, dust, ground coffee
Activities: hiking, drinking, singing
Languages: Polish, Spanish, English
The following countable nouns are abstract:
a hope, a situation, an idea, a nuisance, a remark
Some abstract nouns can only be used as countable nouns:
a statement, a proposal, a denial, a scheme
A lot of uncountable nouns are abstract:
anger, honesty, equality, equanimity