Krsna answers that both He and Arjuna have passed through many births. The only difference is that He knows them all while Arjuna does not know.
Birth and death go on and on until you reach Realisation. During this time your knowledge is confined to your equipments and the environment you are placed in. In other words you know only the present. You cannot tap into the past or penetrate into the future. You know only what your body, mind and intellect perceive now.
You are conscious of perceptions, emotions and thoughts. You are aware of colour and form, feelings and thoughts. You have knowledge of the body, mind and intellect and their interactions with the world. You have no access to objectless Awareness or pure Knowledge.
Pure Consciousness illumines and enables all experiences of the past, present and future. Not just yours but of all living beings including birds, fishes, worms and insects. When you realize your Self you become pure Consciousness. You are then sarvajna and sarvavit. You know everything, everywhere, in all beings.
Arjuna is a limited human being and knows only experiences that come from conditioned consciousness. Krsna is an enlightened Soul. He knows everything.
