riding vs pony-trekking

riding and pony-trekking both are nouns.

Word	Noun	Adjective	Verb	Adverb
riding	Yes	No	No	No
pony-trekking	Yes	No	No	No

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

riding: the sport of sitting on the back of a horse while controlling its movements
pony-trekking: a sport in which people ride across country on ponies

Other hyponyms of riding include equestrian sport.

riding (noun)	pony-trekking (noun)
travel by being carried on horseback	a sport in which people ride across country on ponies
the sport of sitting on the back of a horse while controlling its movements