It is a compound noun. Why? Because 'Back''Pack' is one word, but if you see how i structured it, it can be two. Back, as in your body part, and Pack as in a bag or container, you name it. And just a tip, compound means two words squished into one, ex. CupCake, FireWorks, BaseBall, BasketBall. But when you are typing it, of course, you wouldn't capitalize the first letter of the two words :)
I believe it is a compound noun judging from what google says. This is because compound nouns are a combination of two shorter nouns to make a new noun. For example: Back + pack = backpack. tooth + paste = toothpaste. It is not a proper noun because proper nouns are very specific things. For example the common noun= city, a proper noun could be Los Angeles because it is a specific city. It is not a personal pronoun because those are words that refer to a "person". Examples of personal pronouns are: I, you, he, she, we, them, etc. It is not an intensive pronoun because it is also not refering to a person. Examples of intensive pronouns are: himself, herself, yourself, myself. Hope this helped!
