InterLibrary Loan is a service that the West Library provides to all students free of charge. If there is an resource that is not available at the West Library, either physically or online, then you can request the the West Library staff find a copy of that resource from another library
So InterLibrary Loan is a Library service where you can request resources from other libraries. If you find a resource in WorldCat that you wish to borrow, you can use InterLibrary loan to get it.