Oracle is a relational database management system that is ideally suited for large enterprise applications. It includes grid computing features that enable databases to make use of load balancing features without the need to install any additional software components.
Oracle is available in various editions each designed to meet a different set of requirements. The standard edition contains all the basic database features and functionalities and is meant for a limited number of users. The enterprise edition includes numerous features over and above the standard edition. The Oracle database is also available in an Express Edition that is available for free distribution on Windows and Linux platforms. However the express edition limits the data storage to 4GB. Another edition is the Oracle personal edition that is meant for single users. An Oracle database can also be deployed on mobile devices via the Oracle Database Lite.
Oracle is platform independent and can be deployed on a whole range of platforms including Windows, Linux, Mac OSX, etc.