The hierarchy and the age seen by the Koreans !
Conversations between people are defined by some very specific criteria. First of all, when you meet a Korean, he/she will have a tendency to ask your age at the beginning of your conversation.
It’s not nosiness, he’s just trying to work out his status in relation to you and a suitable level of familiarity. He will choose to speak more formally or informally, and will take the liberty of asking you for certain things, such as going to buy him something to eat, for example. This type of situation may very well occur in the workplace, or in a private circumstance.