A preconfigured environment of subscriptions and resources with identity, governance, networking, and security already in place as a foundation for deploying workloads. It follows the Azure Landing Zones reference model within the CAF, split into platform zones and application landing zones.
AZ-305 asks about designing the management group and subscription hierarchy of a landing zone (e.g., Platform: Management, Identity, Connectivity; Landing Zones: Corp, Online). Azure Landing Zone Accelerator is the reference implementation.
Azure landing zone is a concept that can show up on the exam. Check the full guide to see it in context.