This is the 4276th most frequent Korean word.
초대
Invitation.
In this sentence, '초대' is used as a noun referring to the invitation itself.
나는 친구의 결혼식에 초대를 받았다.
I received an invitation to my friend's wedding.
Here, '초대' is used as a verb meaning 'to invite' someone.
나는 생일 파티에 친구를 초대했다.
I invited a friend to my birthday party.
In this sentence, '초대' is again used as a verb, emphasizing the action of inviting.