1. Demonstrative adjectives and pronouns!!!!!!!!!!!!!!!!!!!!!!!!!
This
These
That
Those

2. This as an adjective This = Este / Esta These = Estos / Estas
This book is good. These books are good.
Este libro es bueno. Estos libros son buenos.
This table is good. These tables are good.
Esta mesa es buena. Estas mesas son buenas.

3. That as an adjective That = Ese / Esa Those = Esos / Esas
That book is good. Those books are good.
Ese libro es bueno. Esos libros son buenos.
That table is good. Those tables are good.
Esa mesa es buena. Esas mesas son buenas.

4. Remember it with this simple rhyme(ish):
This and these have “t”’s
That and those don’t

5. Spanish has a weird, extra that for things that are far away, like China and the moon of Saturn. As an adjective:
That = Aquel / Aquella
Those = Aquellos / Aquellas
That country of China is good-ish.
Aquel país de China es bueno.
That moon of Saturn is good. Those moons…
Aquella luna de Saturno es buena. Aquellas lunas…

6. To turn these things into pronouns, they simply function as nouns and cease to modify any other nouns (or, don’t put ‘em in front of nothin’)
Adjective:
I like this book.
Me gusta este libro.
Pronoun:
I like this one.
Me gusta éste.

7. During some year in the past the Royal Spanish Language Academy decreed that the demonstrative pronoun need no longer bear the accent which previously served to distinguish it from its adjectival cousin.
I will continue to write it because I am a traditionalist.
You don’t have to.

8. This as a pronoun This = Éste / Ésta These = Éstos / Éstas
This one is good. These are good.
Éste es bueno. Éstos son buenos.
Ésta es buena. Éstas son buenas.

9. That as a pronoun That = Ése / Ésa Those = Ésos / Ésas
That one is good. Those are good.
Ése es bueno. Ésos son buenos.
Ésa es buena. Ésas son buenas.

10. The far away that as a pronoun
That = Aquél / Aquélla
Those = Aquéllos / Aquéllas
That one is good. Those are good.
Aquél es bueno. Aquéllos son buenos.
Aquélla es buena. Aquéllas son buenas.

11. “Neuter” pronouns; use these if you don’t know what the thing is or if it’s an entire idea
This = Esto
These = Estos
That = Eso / Aquello
Those = Esos / Aquellos
Wow, that thing’s ugly. What is that?
Uf, esa cosa es bien fea. ¿Qué es eso?
Drinking underage is bad. Yes, that is bad.
El consumo de alcohol de los menores de edad es malo. Sí, eso es malo.

12. Escribir en español Do you like this class?
No, I like those.
Do you like that Kim Jong Un? (way over there in North Korea)
These kids. Am I right?
I see this clown.
I see that clown.
Oh yeah? I see that clown. (farther than the other two)
What is this? Interrupting me class?
What is that? Insolence?