The demonstrative adjectives—this/that/these/those—tell us where an object is located and how many objects there are.
This and that are used to point to one object. This points to something nearby while that points to something “over there.”
This dog is mine.
This is mine.
That dog is hers.
That is hers.
These and those refer to more than one object. These points to things nearby while those points to things “over there.”
These babies have been smiling for a while.
These are mine.
Those babies in the nursery have been crying for hours.
Those are yours.