There are 9 parts of speech or word classes in English language:
– nouns
– pronouns
– determiners
– verbs
– prepositions
– adjectives
– adverbs
– conjunctions
– interjections

Nouns are a group of words that we use to name:
– people: man, woman, teacher, John, Mary
– animals: cat, rabbit, horse, elephant
– plants: palm tree, coconut trees, grass, wheat, corn
– places: home, office, town, village, England
– concrete objects: chair, table, ball, water, money, sugar
– abstract objects: truth, lies, happiness, sorrow, time, friendship

Determiners, prepositions and adjectives are related to the use of nouns.

– Determiners specify a limit to nouns.
I saw a cat.
‘A’ is a determiner.
‘Cat’ is a noun.

– Prepositions specify relations between two nouns.
The cat is under the bed.
‘Under’ is a preposition.
‘The cat’ and ‘the bed’ are nouns.

– Adjectives specify the condition, characteristic, emotion of nouns.
James is sick.
‘James’ is a noun.
‘Sick’ is an adjective.

James is happy.
‘Happy’ is an adjective.

We use determiners in front of nouns or noun phrases.
a cat
the cat
that person
two American citizens
all books
some information

Demonstrative determiners show whether something is near or far from the speaker in the context of space or time.

this:
used for singular countable noun near to the speaker

I like this pen.
I like this pens. (wrong)

I know this person.
I know this people. (wrong)

that:
used for singular countable noun far from the speaker

I like that pen.
I like that pens. (wrong)

I know that person.
I know that people. (wrong)

these:
used for plural countable noun near to the speaker

I like these pens.
I like these pen. (wrong)

I know these people.
I know these person. (wrong)

those:
used for plural countable noun far from the speaker

I like those pens.
I like those pen. (wrong)

I know those people.
I know those person. (wrong)

this:
can be used with uncountable nouns

that:
can be used with uncountable nouns

these:
CANNOT be used directly with uncountable nouns

those:
CANNOT be used directly with uncountable nouns

I like this bread.
I like these bread. (wrong)

I need that information.
I need those information. (wrong)

these:
can be used with quantity expressions to describe uncountable nouns

These pieces of information are important.
These piece of information are important. (wrong)
These information are important. (wrong)

those:
can be used with quantity expressions to describe uncountable nouns

Those pieces of advice are very useful.
Those piece of advice are very useful. (wrong)
Those advice are very useful. (wrong)