This is a secure, scalable, easy-to-manage enterprise portal server that can be used to put information to work, connect people and workspaces and target and tailor information to users or groups. All features of Windows SharePoint Services are available in SharePoint Portal Server 2003.
The server builds on the Microsoft Windows® SharePoint Services platform by using SharePoint sites to create portal pages for people, information and organizations. Businesses can integrate processes and applications, as well as provide a full set of collaboration and personalization features for end-users.
SharePoint Portal Server:

• Adds entire classes of additional functionality to an enterprise, connecting people, teams and knowledge across business processes.
• Integrates information from various systems into one solution with flexible deployment options and management tools.
• Facilitates end-to-end collaboration by enabling information workers to find and leverage people, information and SharePoint sites across the enterprise.
• Delivers personally relevant information through audience targeting and through personalization and customization tools.