I will teach you this knowledge in full, together with realized understanding, leaving nothing out. Once you know it, nothing further remains here to be known.
Explanation
Krishna has just told Arjuna to listen to how he can know him fully; here he promises a complete teaching. Knowledge (jñāna) means understanding learned from teaching, and realized understanding (vijñāna) means that same truth known through direct experience. Krishna says that once this is grasped, nothing more is left to learn. Traditions differ on what "this" covers: some stress knowledge of the one Supreme, others the distinction between spirit and matter.