The adjectives a, an, and
We built a campfire to keep warm.
Have you seen an orangutan swinging?
The road is slippery and icy.
This, that, these, and those are called demonstrative adjectives. We use demonstrative adjectives to tell how close or far away things or people are.
This and that are singular demonstrative adjectives.
This tree is really tall.
(The tree is close.)
That tree stands alone.
(The tree is further away.)
These and those are plural demonstrative adjectives.
These flowers are lovely.
(The flowers are close.)
Those flowers are blooming nicely.
(The flowers are further away.)