There are five editions in oracle 11g

Oracle Database Standard Edition One
Oracle Database Standard Edition One delivers unprecedented ease of use, power, and performance for workgroup,department-level, and Web applications. From single-server environments for small business to highly distributed branch environments, Oracle Database Standard Edition
One includes all the facilities necessary to build business-critical applications.

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Oracle Database Standard Edition
Oracle Database Standard Edition delivers the unprecedented ease of use, power, and performance of Standard Edition One, with support for larger machines and clustering of services with Oracle Real Application Clusters (Oracle RAC). Oracle RAC is not included in the Standard Edition of releases prior to Oracle Database 10g, nor is it an available option with those earlier releases.

Oracle Database Enterprise Edition
Oracle Database Enterprise Edition provides the performance, availability, scalability, and security required for mission-critical applications such as high-volume online transaction processing (OLTP) applications,query-intensive data warehouses, and demanding Internet applications. Oracle Database Enterprise Edition contains all of the components of Oracle Database, and can be further enhanced with the purchase of the options and packs.

Oracle Database Express Edition
Oracle Database Express Edition (Oracle Database XE) is an entry-level edition of Oracle Database that is quick to download, simple to
install and manage, and is free to develop, deploy, and distribute. Oracle Database XE makes it easy to upgrade to the other editions of Oracle without costly and complex migrations. Oracle Database XE can be installed on any size machine with any number of CPUs, stores up to 4GB of user data, using up to 1GB of memory, and using only one CPU on the host machine. Support is provided by an online forum.

Oracle Database Personal Edition
Oracle Database Personal Edition supports single-user development and deployment environments that require full compatibility with Oracle Database Standard Edition One, Oracle Database Standard Edition, and Oracle Database Enterprise Edition.Personal Edition includes all of the components that are included with Enterprise Edition, as well as all of the options that are available with Enterprise Edition, with the
exception of the Oracle Real Application Clusters option, which cannot be used with Personal Edition. Personal Edition is available on Windows 2000, Windows NT,Windows XP, and Windows Server 2003 (32-bit and 64-bit versions). The Management Packs are not included in Personal Edition.