itu

In a sentence

• Buku itu ada di meja.

  That book is on the table.

  Here, 'itu' specifies a noun ('buku') to indicate which book is being talked about.

• Itu adalah pilihan yang baik.

  That is a good choice.

  'Itu' is used as a demonstrative pronoun to refer to the subject under discussion.

• Aku tidak tahu itu ada di sana.

  I didn't know that was there.

  'Itu' functions to refer to a previously mentioned idea or object in the context.