Brief about SPRO:
SPRO stands for SAP Project Reference Object. It is used to configure the setting as per your client requirement by using the standard setting present in the system. This where you can do all the SAP configuration work.
Also, the same be found out merely by searching on the web and SAP Help portal.
SPRO stands for SAP project reference Object , when you execute this transaction you will find an IMG - which is ther for managing the implementations .
So in IMG you can define your own projects and set the scope of the project .
SPRO is used for making necessary customizing in the system for the KDS - Key data structure and Configurations .
Like for Example - Your vendor master is a master data but in vendor master the payment term is a KDS key data structure , so if you want to add a new payment term then you will have to execute the T code SPRO and then navigate to the option of creating a new payment term and define there .
hope this helps .