We can use demonstrative adjectives to help us make reference to a certain object. The easiest way to remember which one to use, is by thinking of distance.
A. When an object is physically close to you, we use este, estos, esta, and estas, which in English would be “this …” or “these…”.

Por ejemplo:

Me gusta esta blusa (que tengo en la mano).
I like this blouse (that I have in my hand).
B. When an object is further away from you, we use ese, esos, esa and esas, which in English would be “that…” or “those…”

Por ejemplo:

Álvaro quiere comprar ese gorro (allí en la mesa).
He wants to buy that cap (that is there on the table).
C. When an object is quite far away, but still visible, we use aquel, aquellos, aquella, aquellas, which in English would be “that one (over there)...” or “those ones (over there)...”

Por ejemplo:

¿Vas a mirar aquellos trajes de baño (al otro lado de la tienda)?
Are you going to look at those bathings suits (way over on the other side of the store)?

Unos ejemplos:

este suéter this sweater
estos suéteres these sweaters
ese suéter that sweater
esos suéteres those sweaters
aquel suéter that sweater (over there)
aquellos suéteres those sweaters (over there)

esta blusa this blouse
estas blusas these blouses
esa blusa that blouse
esas blusas those blouses
aquella blusa that blouse (over there)
aquellas blusas those blouses (over there)

Practiquemos los adjetivos demostrativos en la siguiente página.