An honorific auxiliary verb used to show respect for someone else's action; attached to verbs to describe others' actions politely (somewhat formal/old-fashioned).
校長は式で挨拶をせられた。
The principal gave a speech at the ceremony. (honorific)
お客様はすでにお帰りになり、書類はお預かりせられております。
The customer has already left, and the documents have been received (honorific).
教授は次の講義でその問題について説明せられる予定です。
The professor is scheduled to explain that issue in the next lecture (honorific).