Backoffice systems are the normal E.R.P. computer systems used to record Sales Orders, Purchase Orders, Financial data etc, that help management run a business.
They are termed 'backoffice' as they run 'behind the scenes' and are not normally seen by customers or suppliers.
Customers or suppliers normally only see the printed output from such systems - invoices, order documents, delivery notes etc.
For security purposes, they are not normally enabled for direct access to or from the web.
However, for todays modern business some form of limited automated connection between the web and a backoffice system is desireable in order to speed up customer order processing. It can also provide order and account tracking for 'high value' customers and suppliers.

Many of the older backoffice systems cannot easily provide this level of automation requiring data to be manually entered twice. Examples of typical requirements are:
Online web site taking Customer Orders?
Wanted - automated update of your E.R.P./Backoffice system!

Remote workers needing to enter timesheets, expenses, purchase orders, etc?
Wanted - automated update of your E.R.P./Backoffice system!

Remote workers/customers/suppliers needing to query your E.R.P./Backoffice system?
Wanted - as automated query and result feedback system?