This is the 883rd most frequent Hungarian word.
magáról
"About himself/herself/itself."
Here, 'magáról' is a reflexive pronoun meaning 'about oneself'. It refers back to the subject 'the teacher'.
A tanár magáról beszél a diákoknak.
The teacher is talking about himself to the students.
In this sentence, 'magáról' can be interpreted in context as 'about itself', referring to the trip.
Nem mondott semmit magáról a kirándulásról.
He didn't say anything about the trip.
'Magáról' here functions as part of a formal address, meaning 'about you' in a polite or formal manner.