This is simply version control system.
Basic usage:
1). How to clone from repo?
hg clone http://www.selenic.com/repo/hello my-hello
If everything went gladly, You will see new folder in your current directory called `my-hello` . This is the directory that you have checkout from the repository.
2). How to see revision information?
Go to your checkout folder. (my-hello). And type
hg parents
