Desktop Class - Choose this option if you are installing on a laptop or desktop class system. This option includes a starter database and allows minimal configuration. This option is designed for those who wish to get up and running with the database quickly.
Server Class - Choose this option if you are installing on a server class system, such as what you would use when deploying Oracle in a production data center. This option allows for more advanced configuration options. Advanced configuration options available using this option include Oracle RAC, Automatic Storage Management, backup and recovery configuration, integration with Enterprise Manager Grid Control, and more fine-grained memory tuning, among many others.