A Material Request is a simple document identifying a requirement of a set of Items (products or services) for a particular reason.

A Request for Quotation is a document that an organization sends to one or more suppliers asking a quotation for items. System also provides suppliers portal. 

A Purchase Order is a binding contract with your Supplier that you promise to buy a set of items under given conditions. It can be generated directly from Sales Order as well.

Purchase Invoice can be raised from the system before or after delivery.

Partial Invoicing can be done by the system.

Delivery Note can be generated after sales order, sales invoice or directly by skipping these stpes.

Delivery Note can be generated partially respective to the deliveries.