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Invoice
A System Object definition that is intended to allow end Users to track invoices or bills sent by Vendors who provide their organization with goods or services. Invoices are automatically available as a system Block in Object Views for Custom Objects.
Involved
A System Object definition that is always related to a Custom Object. It is intended to allow end Users to keep track of various involved parties associated with a Project. Involved is automatically available as a system Block in Object Views for Custom Objects.