This is the 28th most frequent Catalan word.
això
"That" or "this" (used to refer to something near or previously mentioned).
In this sentence, 'això' functions as a demonstrative pronoun, referring to a specific object (the book) and pointing it out.
Això és un llibre interessant.
This is an interesting book.
Here, 'això' is used as a demonstrative pronoun in a question context, representing something whose nature is asked about.
Què és això?
What is this?
In this context, 'això' is employed as a demonstrative pronoun referring to the content or idea of what is being explained.