This is the 11743rd most frequent Korean word.
내기를
A bet or wager.
Here, '내기를' refers to placing a bet or wager.
내기를 걸었더니 친구가 이겼어요.
I made a bet, and my friend won.
In this case, '내기를' represents the activity of betting in general.
내기를 좋아하는 편은 아니에요.
I am not the type of person who likes betting.
'내기를' here is used to indicate a friendly and casual bet.