No Approvals: You don't need to have invoice approvals setup to use Plate IQ.  It's okay not to.  Without approvals, after invoices are mapped or otherwise triaged in Needs Attention, they'll move to Pending Export.

Single Approvals: This provides the ability to review and approve invoices before they get ready for export.

Advanced Approvals: This allows you to define specific rules that, should an invoice match, would require a list of Potential Approver's approvals.