A delegate is a nominated individual who can perform tasks on another’s behalf. In Catalog we have two types of Delegate: Request Auto-Delegation and Delegate Use of Catalog.
- Request Auto-Delegation is designed to be used when an approver is unavailable – the Delegate will be given the ability (and notification) to perform the approval actions that the user has assigned.
- Delegate Use of Catalog is designed to be used when the user is a requester – they have the right to view the user’s Request Catalog, and raise requests on their behalf.
So one way to think about this is that you're granting the named user a limited right to impersonate the user that the value is set for; either as an approver or requester. It doesn't grant them any other special privileges, such as to approve the user's requests if they don't have that already.