Hi Umer,
PROACT is mainly used to send Inventory data to Suppliers. Its like MMBE data that you see in ECC is sent to Suppliers so that they can plan their production better and also can replenish your Inventory by creating Replenishment Purchase Order.
This IDOC is mainly used in SAP SNC or other SAP products where Vendors Manage your Inventory.
Hope this helps.
Regards,
Shahu