Question

Nowadays people make frequent use of the term "halakhic ruling" and its various forms.
What is the basis of halakhic ruling?
Knowledge? (The rabbi knows more than ordinary laypeople.)
Is the halakhic decisor like a professional who knows things that the layman does not know?
Authority? (The rabbi issuing the ruling received valid authority to decide for others what is permitted and forbidden.)
From the old responsa literature, one gets the impression that when turning to a rabbi who gives practical rulings, the focus is on knowledge, not authority.
And when there is knowledge, the feeling arises that the person with that knowledge is also the one who is "qualified."
What are the sources in general for this term, "halakhic decisor"?
As I recall, in old responsa people address the rabbi with the words "may our rabbi/teacher instruct us," and those words are understood as expressing a desire to know what is unknown to the questioners, not as a request for the exercise of authority.