Inventory module can be used to track the stock of items. Items can be identified by unique serial numbers. Using that unique numbers inventory system can keep track of item and trace its current location in organization.
e.g. you have purchased 100 hard disk , so using inventory system you can track how many hard disks are installed , where they are installed, how many hard disks are remaining etc.
Inventory module includes functionalities like inventory control, master units , stock utilization reporting etc.
There may be integration of inventory module with purchase module of ERP.