My Answer: It receives all the Light that was present in the first stage, but besides this, it has one important addition: It not only wants to receive the Light, but it also wants to attain the Creator’s very status. It wants to become just like Him; in addition to enjoying the Light, it wants to enjoy the position of the Giver!
This can be understood through a parable about a rich man who meets a pauper, and they realize that they were childhood friends. So, the rich man invites the poor one into his home, dresses him in the best clothes, feeds him with the best food, and wants to keep him in his home forever, and to give him everything he could possibly wish for.
However, his friend is sad. When the host asks him, “What else can I do for you?” the other replies, “I don’t want to feel like I’m the receiver. I want to feel like you.” But that is something the rich man cannot provide for him even if he were to give his poor friend everything.
Thus, because the fourth stage of creation was in this state, lacking independence, it decided to cease receiving the Light and performed an action called Tzimutzum Alef – the First Restriction. It thereby cut itself off from the Creator and became independent.
After that, creation’s (our) further development is all about how to become similar to Him.