A spark is a result of two hard objects colliding.
The Creation is a result of the interaction between the Light colliding with the curtain, the resistance of the vessel, since it does not want to receive free gifts.
The Returning Light created the Beings of the Holy System, all different kind of souls that composed Adam. Those Sparks fell into the Kelipot of Darkness as aresult of the Sin. Our journey is about cleansing those sparks.