Backpacking can be a noun or a verb (gerund).
Verb: They went backpacking this weekend.
Gerund/Noun: Backpacking is a fun activity to do as a family.
I'm not sure if it is used as a participle or not. (Because ending in -ing and everything.)
Mini backpacks are often referred to as "mini backpacks" or "small backpacks."
The part of speech for this particular word is a noun.
part of speech
The part of speech for "answer" is a noun.
adverb
what part of speech is beneath
The part of speech for "unfamiliar" is an adjective.
The part of speech of "came" is a verb.
The part of speech for "twirl" is a verb.
The part of speech for "explicit" is an adjective.
The part of speech for "indefinite" is an adjective.
The part of speech for "lecturer" is a noun.