your
The Italian word 'tuo' is used in the same parallels as the English word 'your'. It refers to a specific person or thing that belongs to one or more people. However, because Italian is a language with gender and plurality considerations, you may also see 'tua', 'tuoi', and 'tue' depending on the gender and plurality of the noun this word modifies.
This is your book
This sentence is a usage of 'tuo' in a possessive sense. Here, 'tuo' is used to indicate that the book belongs to the person to whom the speaker is talking.
Your father is very kind
In this sentence, 'tuo' is again used in the possessive sense. It shows that the father, who is a kind person, belongs to the person to whom the speaker is talking.
Where is your pen?
This sentence is a question where 'tua' is used as a possessive pronoun for a feminine noun. The speaker is asking the listener about the whereabouts of their pen.