The description mentioned seems to refer to a type of IPv6 addresses, but there is a small error in their identification. Addresses starting with fc00::/7 are actually part of a range reserved for Unique Local Addresses (ULAs)not for Link-Local Addresses.

The directions Link-Local in IPv6 they start with fe80::/10.

Unique Local Addresses (ULAs) fc00::/7

• Use: The ULAs (fc00::/7) are similar to private addresses in IPv4 (such as 192.168.x.x, 10.x.x.x). They are designed to be used within private networks and should not be routed on the public Internet.
• Routeability: Although ULAs are not routable on the Internet, they are completely routable within private networks or between multiple sites that are under the control of the same administrative entity, using VPN or similar connections to link those sites.
• Purpose:: They provide stability and flexibility in the assignment of addresses within organizations or between sites operated by the same entity that does not depend on an assigned global IPv6 address space.

Link-Local Addresses fe80::/10

• Use: Link-Local addresses (fe80::/10) are automatically configured on all IPv6-enabled interfaces and are used for communications within the same physical network (link segment) and are not valid outside of that context.
• Routeability: These addresses are not routable and cannot be used to communicate between different subnets or network segments.
• Purpose:: Used for local network operations, such as device configuration, neighbor discovery, and for the operation of some routing protocols.

Conclusion

• ULAs (fc00::/7): Routable within private networks but not on the Internet.
• Link-Local (fe80::/10): Not routable outside the local link.

Both types of addresses have important roles in the management of IPv6 networks, but their use and routeability are clearly delimited to avoid connectivity and security problems.