After getting enough reps (I am not sure how much), one can create tags.
What is the procedure to add small description to the tag?
What is the procedure to make synonyms? Eg: EU and European union.
Thanks in advance for your time.
You can create tags on this site after reaching 150 reputation. You can do this simply by adding the new tag to a question - it will be created automatically.
To add a description to your tag, you can visit the tag's 'About' page. In your case, you have created the chinese-communist-party tag, and you can find this tag's information here. Any registered user can suggest edits to this information, and trusted users (4k rep) can have edits approved automatically.
Ideally, a tag should have a tag wiki and usage guidance. Details on what these should contain can be found here.
In order to propose synonyms to a tag, users require the 'create tag synonyms' privilege which is granted at 1,250 rep. They also require an answer score of 5 on the tag. These are then voted on by other users with the requisite answer score. You can also make a post on meta to suggest a synonym if you're not sure, or don't have the requirements to propose a tag synonym, after which a mod may implement your suggestion.