This, That, These, and Those are called Demonstratives. We use these specifically to point at people and things. It can also demonstrate and take the place of certain pronouns or subjects. They can also demonstrate the plurality, singularity, and distance of a person or object.
This is generally used for expressing only 1 object or person that is close to you. Although you could use it to express a singular group of people.
Examples:
This is a cup.
This is my group of friends.
That is similar to This the only difference is how far away the person or object is.
Examples:
That is my friend over there.
That is my car in the parking lot.
These changes as to how many objects or people that are near you.
Examples:
These are my pens.
These are my siblings.
Those demonstrates objects and people that are plural and far away.
Examples:
Those are my keys.
Those people keep looking at us.
The structure is fairly simple.
Note: In some cases, it is common to use Possessive adjectives like my, or your. As well it is common to use Articles like A, An, or The for singular things.
Demonstrative + Verb to be + Object + Compliment.
Examples:
This is my car.
These are the keys.
Demonstrative + Verb to be + Not + Object + Compliment.
Examples:
That is not my house.
Those are not yours.
Verb to be + Demonstrative + Object + Compliment?
Examples:
Is that the dog?
Are those our tickets?