What is state within state?

"State within a state" refers to a situation where an entity or group operates independently from the central government, often possessing its own authority, governance structures, or control over certain regions. This can manifest in various forms, such as armed groups, separatist movements, or powerful political factions that challenge the state's authority. Such dynamics can lead to instability and conflict, as the central government may struggle to assert control over these autonomous entities. Examples include regions with significant autonomy or influence, like Catalonia in Spain or various regions in conflict-affected countries.