riding vs pack riding

riding and pack riding both are nouns.

Word	Noun	Adjective	Verb	Adverb
riding	Yes	No	No	No
pack riding	Yes	No	No	No

As nouns, pack riding is a hyponym of riding; that is, pack riding is a word with a more specific, narrower meaning than riding:

Other hyponyms of riding include bronco busting, endurance riding, trail riding.

riding (noun)	pack riding (noun)
travel by being carried on horseback	riding with a pack
the sport of sitting on the back of a horse while controlling its movements