This is the 1068th most frequent Russian word.
подтвердил
"Confirmed."
The word 'подтвердил' here is used to indicate that he affirmed or validated his joining of the event.
Он подтвердил свое участие в конференции.
He confirmed his participation in the conference.
The word 'подтвердил' in this sentence means verifying or assuring that a stated fact or plan is true or will occur.
Генеральный директор подтвердил, что проект будет завершён вовремя.
The CEO confirmed that the project will be completed on time.
Here, 'подтвердил' denotes the act of verifying or corroborating information against a reference.