It is anything with which you have identified yourself. In technical language, we call this kind of self, gaunatman , a secondary and foisted self. An object cannot become you. Yet, we do nothing but that. We identify light with darkness, darkness with light, the subject must become the object in order that it may be an object of love.
Love is nothing but the subject becoming the object.
And Acharya Sankara says this cannot be, and we are saying that this has to be. So, here, we are in this world of terrific difficulties, created by whom, no one knows. This gaunatman , this secondary self, is the object of affection and aversion, which are two sides of the same coin. Let each one ponder deeply in one's heart. The Self , in one way, as I pointed out, is that with which you have identified yourself.