Credit delegation is a feature that helps organizations manage their credits effectively. The default setting for most organizations is having credit delegation disabled. This means all administrators in that organization's account simply share all of the credits the organization has purchased (think of the organization's credits as one big shared pool of credits and any administrator can use as many credits as they need or want).
For some organizations, the above approach works well to have one shared pool of credits available that any administrators can access.
For other organizations, this approach might be problematic so the credit delegation feature is used. By enabling the credit delegation feature for a specific administrator account, the administrator now has their own individual pool of credits and two things are accomplished:
The administrator is limited or restricted to the number of credits in their individual pool which can help prevent overuse of credits.
The delegated credits are reserved and can be used by only that administrator which helps guarantee the amount of credits that administrator can use since no other administrators can.