Hi, Setenta, I'm trying to explain you with a lot of examples for you to understand very well and definitely:
★ Spanish has three words where English only has two. In English, we say "this" or "that" depending upon whether the object is close to us or not. In Spanish, we also say "this" and "that," but there is another separate word used to mean "that one over there." This form is used when the object is more than just a short distance away, for example, on the other side of the room. Here are the three forms for "this" "that" and "that one over there."
→ este (this)
→ ese (that)
→ aquel (that one over there)
★ The demonstrative adjectives have four forms: masculine singular, masculine plural, feminine singular, feminine plural.
→ este libro (this book)
→ estos libros (these books)
→ esta pluma (this pen)
→ estas plumas (these pens)
→ ese libro (that book)
→ esos libros (those books)
→ esa pluma (that pen)
→ esas plumas (those pens)
→ aquel libro (that book over there)
→ aquellos libros (those books over there)
→ aquella pluma (that pen over there)
→ aquellas plumas (those pens over there)
★ Here are the corresponding demonstrative pronouns:
→ este (this one - masculine)
→ estos (these ones - masculine)
→ esta (this one - feminine)
→ estas (these ones - feminine)
→ ese (that one - masculine)
→ esos (those ones - masculine)
→ esa (that one - feminine)
→ esas (those ones - feminine)
→ aquel (that one over there - masc.)
→ aquellos (those ones over there - masc.)
→ aquella (that one over there - fem.)
→ aquellas (those ones over there - fem.)
★ Each demonstrative pronoun also has a neuter form. They do not change for number or gender, and they are used to refer to abstract ideas, or to an unknown object.
→ esto (this matter, this thing)
→ eso (that matter, that thing)
→ aquello (that matter / thing over there)
I really hope this helps you, Setenta. All the best!