The blood clot. A blood clot protects the socket. After tooth extraction, it's important for a blood clot to form to stop the bleeding, infection and begin the healing process. Just follow the surgeon's instructions.
Extraction healing. It is not normal for a clot to dissolve following tooth extraction. That would generally lead to a dry socket and pain. The clot actually reorganizes and matures leading to the formation of bone and wound healing. Here is a good website that describes the process: