In Spanish, demonstrative adjectives like este, esa, and aquellos always accompany a noun. But when the noun is unknown, abstract, or not mentioned, Spanish switches to a different set of words: esto, eso, and aquello. These are neuter demonstrative pronouns -- not adjectives -- and they never modify nouns. Instead, they point to ideas, feelings, or unnamed things.
To read a more in-depth explanation, go to Span¡shD!ctionary.com and check out
The Neuter Demonstrative Pronouns “Eso,” “Esto,” and “Aquello”
To practice using Demonstrative Adjectives, go to Practice Sheet for Demonstrative Adjectives.