In 1 Kings 4:1–6, a number of titles of officials are mentioned (ESV):
King Solomon was king over all Israel, and these were his high officials: Azariah the son of Zadok was the priest; Elihoreph and Ahijah the sons of Shisha were secretaries; Jehoshaphat the son of Ahilud was recorder; Benaiah the son of Jehoiada was in command of the army; Zadok and Abiathar were priests; Azariah the son of Nathan was over the officers; Zabud the son of Nathan was priest and king’s friend; Ahishar was in charge of the palace; and Adoniram the son of Abda was in charge of the forced labor.
What kind of official is "the king's friend", said of Zabud in v. 5?