Here's why:
* Participial phrases are groups of words that act like adjectives, modifying a noun or pronoun. They are formed from a participle (a verb ending in -ing or -ed) and its modifiers.
* In this sentence, "left behind" is the past participle of the verb "leave".
* It modifies the noun "jewelry", describing the kind of jewelry being discussed.
Let me know if you'd like to practice with more examples!