A Quotation is the first stage in creating a sale. The `New Sale` area creates a quotation and when All sales start of as a Quotation
A revision is a copy of a quotation. They are useful in keeping a record of how a quotation has changed before the final invoice or delivery note is created. Revisions are created by selecting Save Revision
from the save menu.
The checkout area is used to reserved stock for a customer. It is the intermediate state between a quotation and an invoice. When a sale is 'checked out' items added or items removed will all affect the `stock on hand`.