A(Gab) and B(Eul) refer to people to make a contract or to affiliate on a written contract.

'A(Gab in Korean)' refers to a person who has an advantageous position comparing to 'B(Eul in Korean)' refering to a person in the position of disadvantage on contract however this word has been streched to the definition of the relationship between the strong and the weak.

This is one of the reprentive example to show Korean social hierachy.