the receptive helper verb is a verb that fits onto the あ stem
「れる」 for godan verbs
「られる」 for ichidan verbs
the receptive helper verb mean to receive the action of the verb to which it is attached
ex: 「叱る」 means “to scold”, 「叱られる」 means “to get scolded”, and 「叱られた」 means “got scolded”
while the potential helper verb can be though of as an engine car (along with the verb to which it is attached), the receptive helper verb cannot (because the action of the first verb is done by someone different)
the real action of the sentence is in 「れる」/「られる」, not the verb to which the receptive helper verb is attached
ex: 「彼は誰かにカバンが盗まれた。」
the 「カバン」 is what receives the action of getting stolen (「盗まれた」)
the に particle in this sentence marks the thing from which something is being received (in other words, it marks the source of the received action)
ex: 「彼が誰かにカバンを盗まれた。」
this changes the previous example to use the “nuisance receptive”, 「彼」 is now the が-marked receiver of the action