Questo can be a demonstrative adjective meaning “this” (when singular) or “these” (when plural):
Questo gatto è curioso. = This cat is curious.
Questi gatti sono curiosi. = These cats are curious.
As an adjective, questo has five forms. It will always precede the noun it modifies and agree in gender and number:
*If your singular noun begins with a vowel, questo is often elided and the final vowel of questo is replaced with an apostrophe, e.g.,
Quest’anno vado a Cortina.
This year I am going to Cortina.