parallel bars vs exerciser

parallel bars and exerciser both are nouns.

Word	Noun	Adjective	Verb	Adverb
parallel bars	Yes	No	No	No
exerciser	Yes	No	No	No

As nouns, exerciser is a hypernym of parallel bars; that is, exerciser is a word with a broader meaning than parallel bars:

parallel bars: gymnastic apparatus consisting of two parallel wooden rods supported on uprights
exerciser: sports equipment used in gymnastic exercises

Other hypernyms of parallel bars include gymnastic apparatus.

parallel bars (noun)	exerciser (noun)
gymnastic apparatus consisting of two parallel wooden rods supported on uprights	sports equipment used in gymnastic exercises