Questo/questa (this), and quello/quella (that) are both adjectives when they come before a noun or pronoun, and pronouns when replacing a noun. This happens in both English and Italian.
In the following examples, we have adjectives.
In questo caso, perché uso il congiuntivo?
In this case, why do I use the subjunctive?
Caption 10, Corso di italiano con Daniela - Il congiuntivoPlay Caption
Questa storia vuole dire che bisogna imparare dalle esperienze degli altri.
This story means that you need to learn from the experiences of others.
Caption 24, Adriano - FiabaPlay Caption
Quella donna ha sempre avuto un aria un po' triste, poveretta.
That woman has always had a sad air about her, poor thing.Play Caption
In the following example, quello is shortened to quel but it works the same way.
In quel caso non ho bisogno della preposizione.
In that case I do not need the preposition.Play Caption
If there were an “S” plus “P” in a masculine noun, as in the following example, we might say:
Luigi ha quello spirito di avventura che io non ho.
Luigi has that spirit of adventure that I do not have.
As a pronoun, questo, questa, quello or quella may replace both objects and people. In some cases, it’s true in English, too, as in:
Questo è per te.
This is for you.
Here, in the same sentence, we have the pronoun and person the pronoun refers to.
Questa è mia zia.
This is my aunt.
But attenzione. In Italian, we can use the pronoun form to replace people or things even when in English we need the adjective form plus a pronoun. In the example below, questo is a pronoun, representing “this person” but in English, we need to use the adjective “this” plus the pronoun “one” that stands for a person we aren’t identifying by name. We could also say “this guy” or “that guy.”
Questo è pazzo completo, or more correctly, [questo è completamente pazzo]
This one/this guy is completely crazy.
Caption 23, Il Commissario Manara - S2EP2 - L'addio di LaraPlay Caption
So watch out for examples such as the above, where the Italian pronoun corresponds to an adjective plus pronoun in English.
La sua scrivania è quella là, dottoressa.
Your desk is that one over there, ma'am.Play Caption
In English, we could say, “That’s your desk,” but it would be wrong to say, “Your desk is that over there.”
Uno di loro, per l'esattezza quello che voleva tagliarti la gola...
One of them, to be precise, the one who wanted to cut your throat...Play Caption
Sometimes, questo, questa, or quello, quella represents something unspecified and we might translate it as “what,” or “whatever.”
"Se fossi in te io non lo chiamerei,
“If I were you, I would not call him,
poi tu fai quello che ti senti di fare".
but you do whatever you feel up to doing.”
Captions 64-65, Marika spiega Gli avverbi - Avverbi di tempoPlay Caption
When using these adjective/pronouns, we just need to remember that they work similarly in English and Italian, but only up to a point. What's been discussed here is a detail, but it can easily trip us up when we're trying to speak our best Italian or understand what someone is talking about.
As you watch Yabla videos, see if you can determine when questo, questa, quello and quellabehave as adjectives and when they are pronouns. Don’t forget that you can also click on the transcript of a video and see the whole text printed out in one or both languages. It may be easier to pick them out.