I was asked to differentiate between helping verb & auxiliary verb but I couldn’t. I doubt it was a trick.
One of my friends was asked to differentiate between them. Surely "an interviewer" since he is a job seeker & I think the interviewer did try to trick him, IMO. Then he asked me but I preserved to answer him to avoid making mistake.
You declined/refused to answer.Then he asked me but I preserved to answer him to avoid making mistake.
There is no difference between 'helping' and 'auxiliary' verbs. The former term is less formal, that's all.