A. Enterprise Resource Planning software, or ERP, doesn't
live up to its acronym. Forget about planning?it doesn't do
much of that?and forget about resource, a throwaway term.
But remember the enterprise part. This is ERP's true
ambition. It attempts to integrate all departments and
functions across a company onto a single computer system
that can serve all those different departments' particular
needs.
B.
Building a single software program that serves the needs of
people in finance as well as it does the people in human
resources and in the warehouse. Each of those departments
typically has its own computer system optimized for the
particular ways that the department does its work. But ERP
combines them all together into a single, integrated
software program that runs off a single database so that the
various departments can more easily share information and
communicate with each other. thats why it has the inventory.

ERP is the software used as a Business management tool. 
Actually inventory comes under MRP. But ERP deals with all 
the modules like HR Module , Accounting Module etc.. one 
module among these is MRP. Hence Inventory is included in 
ERP.

ERP -stands for Enterprise Resource Planning 
Eg:SAP,oracle applications...etc
Enterprisse means entire system of company.
For example if if you take a company company issues  are
Human resource management(HRM),Customer relation ship 
management(CRM),Inventory management,Insurance management
for the employees and the company assets...etc
 
i think edwin r u clear with this answer
 if want still more mail me i can forward some more 
important information for you.

mail me at:rajendra_penumalli@yahoo.com

ERP consists of several related modules grouped and 
integrated together in one system or application using same 
database, application and web servers. Examples of ERPs by 
different organisations/brands are:-

1) Oracle - HR, Financials, CRM etc
2) PeopleSoft - HCM, Financials, CRM, SCM etc
3) SAP - HR, FICO, SD, MD etc

Hope with this you will understand generally what ERP is ? 
if not let me know bvsmreddy@yahoo.com