Final answer:
Enterprise portals come in three forms: Intranet, which is used internally; Extranet, which provides limited network access to external users; and Internet, which is publicly accessible.
Step-by-step explanation:
Enterprise portals can indeed take one of three forms which are Intranet, Internet, and Extranet. Intranets are used internally within a company, enabling employees to access and share information within the organization. Externets allow limited company network access to external users, usually for specific purposes like collaboration with business partners or vendors. The Internet portal is open for public access and provides a gateway to the broader digital world. These portals are essential for various business activities including collaboration, document sharing, and communication.