An ATG Portal Developer specializes in designing, developing, testing, and deploying web applications using Oracle's ATG Web Commerce platform. They handle tasks like customizing the platform to meet business needs, integrating it with other systems, and troubleshooting issues. They also work on improving the user interface and user experience, enhancing site performance, and ensuring the security of the portal. They collaborate with other development team members, designers, and stakeholders to deliver high-quality web solutions. Additionally, they may be involved in maintaining documentation and providing technical support for the ATG portal.