One talks to either share knowledge or to acquire knowledge. Acquisition of new knowledge happens when one listens carefully, questions it for clarifications, analyses it with reference to what one knows, internalises it based on personal reconfirmation and creates an mindful intention to store it for our future use. Sharing is usually meant for others but also can be used as a reconfirmation of what one knows. This is based on how others accept or reject or fine tune the piece of knowledge you have shared. However, sharing should be done only when the other person is open to listening and engaging in a productive manner else it becomes a useless exercise. One needs to judge this during a conversation before continuing the sharing. The art of not talking is as important as when to talk.