can pls give information abt some words freqtly used in sd ,mm

1pls tell definitions of the purchase requistiton,purchase order andwhat is shippment notice,shippment type.

2sd flow :1 enquiry 2quotation 3sales order 4delivery 5billing i6nvoice

is this sd flow is correct and describe each step in this flow

3what is the difference b/w invoice and billand bill of payment

4what is the purpose of the grn report and what is GRN (goods receipt notice)

5 what is the delivery note ?

what is the pupose of tcode mf01 (goods received)