A set of specifications for a system, or Configuration Item (CI) within a system, that has been formally reviewed and agreed on at a given point in time, and which can be changed only through change…

The definition provided perfectly describes a "Baseline Configuration," which is a formally established and approved set of specifications for a system or component at a specific time. This baseline acts as a foundational reference point for all subsequent changes, ensuring that modifications are controlled and tracked to maintain system integrity.

System configuration is a broader term referring to the current setup of a system, which may or may not be formally baselined or subject to strict change control.

Configuration management is the process of establishing and maintaining consistency of a product's performance, functional, and physical attributes, of which creating baselines is a part, but it's not the baseline itself.

Software configuration specifically refers to the settings and setup of software, which is a subset of a baseline configuration for a whole system or CI.