What is what does it mean when a boy says k?

"K" is a shorthand way of saying "Okay." It is typically used as a response in text messages or instant messaging when someone wants to acknowledge that they have received a message or task, but do not have much else to say about it. It can be seen as a casual and dismissive response, as it can be interpreted as a lack of interest or engagement in the conversation. However, it can also be used as a way to quickly and efficiently communicate agreement or understanding in a conversation.