How to version a project?

Question

I want to know how to version project? In x.x.x (three numbers) format or x.x.x.x (four numbers)? And what are the numbers introduce (e.g. third number show bug fixes)?
* I'm using git, if you know about git, please talk about "git tag".

Answer 1

This should help you out, it's an article with a good overview of semantic versioning.

http://www.jvandemo.com/a-simple-guide-to-semantic-versioning/

Answer 2

Thank you so much.
If you have any problems, I wish to help you next time. Thanks a lot.