A commonwealth is a group of people or of groups with a common aim to improve themselves, help each other and share knowledge and resources.
The word can refer to several organisations:
The Commonwealth of Nations, the countries linked with the United Kingdom usually speaking English The Commonwealth of Independent States was the collection of countries which were part of the Soviet Union
It is also part of the official name of some countries
The Commonwealth of Australia
or part of the official name of some US states and territories
The Commonwealth of Pennsylvania
The Commonwealth of Virginia
The Commonwealth of Massachusetts
The Commonwealth of Kentucky
The Commonwealth of Puerto Rico
In history the Commonwealth of England was the name of England between 1649 and 1660, when England had no king.