SAP is it ERP …? Yes correct .. but not totally correct if you talk SAP is part of ERP Software (Enterprise resource planning (ERP) and SAP is an enterprise resource planning (ERP) software product capable of integrating multiple business applications, with each application representing a specific business area. These applications update and process transactions in real time mode. It has the ability to be configured to meets the needs of the business. But ERP is not (only) SAP

I have found simple explanation about ERP on Wikipedia http://en.wikipedia.org/wiki/Enterprise_resource_planning

ERP (Enterprise Resource Planning) systems attempt to integrate several data sources and processes of an organization into a unified system. A typical ERP system will use multiple components of computer software and hardware to achieve the integration. A key ingredient of most ERP systems is the use of a unified database to store data for the various system modules.

The two key components of an ERP system are a common database and a modular software design. A common database is the system that allows every department of a company to store and retrieve information in real-time. Using a common database allows information to be more reliable, accessible, and easily shared. Furthermore, a modular software design is a variety of programs that can be added on an individual basis to improve the efficiency of the business. This improves the business by adding functionality, mixing and matching programs from different vendors, and allowing the company to choose which modules to implement. These modular software designs link into the common database, so that all of the information between the departments is accessible in real time.

ERP Software not only SAP you can find any kind ERP Vendor such as Sage Accpac ERP, please visit http://en.wikipedia.org/wiki/List_of_ERP_software_packages