The Architecture Landscape is divided into levels known as Segment Strategic and Capability Architectures.
These levels correspond to different scopes and purposes of architectures within an enterprise. Segment Architectures are architectures that address specific business units, functions, or processes within an enterprise. Strategic Architectures are architectures that provide a high-level view of the enterprise's vision, goals, and direction. Capability Architectures are architectures that address specific business capabilities or services that span multiple segments or domains. Reference: The TOGAF Standard | The Open Group Website, Section 2.4 Architecture Repository.

Gap analysis is a technique that is used to validate an architecture by highlighting the shortfall between the Baseline Architecture and the Target Architecture. One of the purposes of gap analysis is to identify missing functions that are either deliberately omitted, accidentally left out, or not yet defined in the Target Architecture. Missing functions are marked as gaps that need to be filled by developing or procuring the building blocks.

In the context of TOGAF, a stakeholder is any individual, team, or organization who has interests in, or concerns relative to, the outcome of the architecture. Concerns are those interests which pertain to any aspect of the system's functioning, development or operation, including considerations such as performance, reliability, and security1. References:
*The TOGAF Standard, Version 9.2 - Definitions - The Open Group

When considering agile development,Architecture to Support Portfoliowill identify the necessary products for the enterprise, define their boundaries, and outline the constraints for a product owner. This process directly relates to defining the enterprise'sbacklog, which in agile methodologies, is a prioritized list of work for the development team that is derived from the roadmap and its requirements.

A-Architecture Repository: This is a part of the Architecture Metamodel that contains artifacts structured according to the metamodel. It includes the Architecture Landscape which is adopted by the enterprise and governed by certain standards and practices.
B-Governing Board: The Governing Board ensures visibility and escalation, meaning it oversees and manages the capability of the architecture landscape. It plays a crucial role in governance.
C-Enterprise Capability: This refers to how well an enterprise can execute its mission, meet business objectives or satisfy its stakeholders' needs and expectations. It's influenced by both internal factors (like resources, processes) and external ones (like market trends).
TOGAF Version 9.1, Chapter 34: 1