This is the 2844th most frequent Japanese word.
いらっしゃる
"いらっしゃる" is a respectful term meaning "to go," "to come," or "to be (exist)," used for someone of higher status.
In this sentence, いらっしゃる is used as a respectful verb expression to describe the teacher's presence.
先生がこの教室にいらっしゃいます。
The teacher is in this classroom.
Here, いらっしゃる is used as a respectful verb expression in a question when asking about someone's attendance.
田中さん、明日の会議にいらっしゃいますか。
Mr. Tanaka, will you attend tomorrow's meeting?
In this case, いらっしゃる is used in its imperative polite form to invite someone respectfully.