The four essential features of a state are territory, population, sovereignty and government. The people who make up a state are often the key component; states with populations sharing similar political and social views tend to be the most stable.
The territory of a state refers to its definitive geographical boundaries. They may, however, change over time due to due to dispute, war outcome, purchase or negotiations between governments.
Sovereignty refers to the absolute authority of the state to make laws and enforce them throughout the entire territory without approval from a higher power. The government is responsible for maintaining social order, providing public services and enforcing decisions its citizens must abide by.