Can you explain the difference between Object repository and object spy in QTP?

Object repository contains the recorded object and its information. It’s a container of objects that can be changed as required by the script.
Object spy is the one that can be use to check the objects and object properties in the application. A head with a hat symbol indicates the object spy in QTP. When some objects are not generated / recognized in the script while recording. In this case we normally go for object spy option in QTP.