Apposizione is a word or a group of words that helps defining a noun, giving more info about it, just like an adjective gives more info about a noun or an adverb defines the quality of a verb. Apposizione is often made of a noun or an adjective or both and it is often introduced by an article. Apposizione could be seen also as a "nickname" that doesn't replace the noun but it is added after the noun. You can understand how "apposizione" is used, by analyzing the text.
"Coll'apposizione". (coll' = con l' = with). With nouns together with an apposition (apposizione), that is when they declare or determine the preceding noun in a general manner. They recognized Arione sonatore di cetra (player of zhiter, a musical instrument) (here "sonatore di cetra" is an apposizione). Adriani il giovane (the young) (here "il giovane" is an apposizione). - Guys joyfully surrounded Agnese, their old friend. Manzoni. - The door was closed, sign that the boss was having dinner. Manzoni.