In game AI, a blackboard is a shared memory structure used by multiple behaviours, planners, or services. Instead of every subsystem holding isolated copies of the same information, the blackboard provides one common place for facts such as “enemy visible”, “last known position”, “current target”, or “squad order”. Millington includes blackboards as one of the classic AI infrastructures for coordinating multiple decision systems, and later production examples often use blackboard-style stores inside behaviour-tree or utility-based frameworks. (Millington, Artificial Intelligence for Games, see source-artificial-intelligence-for-games; Hanlon and Watts, Game AI Pro 360: Guide to Character Behavior, see source-game-ai-pro-360-character-behavior)
The main benefit is coordination. The main risk is hidden coupling: when too many systems write to the same shared data, debugging becomes difficult.
Full concept page: blackboard-architecture
Related: behaviour-trees, game-ai-agent-design, utility-ai, squad-ai-patterns, ai-architecture-patterns