The Commonwealth is an organization consisting of the United Kingdom and most of the countries that were previously under its rule.
Commonwealth is used in the official names of some countries, groups of countries, or parts of countries.
...the Commonwealth of Australia.
...the Commonwealth of Independent States, which replaced the Soviet Union.
If you refer to a commonwealth of nations, you are referring to a group of countries who are friendly towards each other and have something in common.
...a commonwealth of nations without economic borders.
There is relatively little information about commonwealth, maybe you can watch a bilingual story to relax your mood, I wish you a happy day!