If you visit someone's GitHub profile you could only see their profile picture, a description they provided, their popular/pinned repositories, and some links and details like - location, company, twitter link. Here is how my profile used to look like(maybe yours look like this as well):
But, now with this new secret feature, you can add a custom intro to your page. Mine looks like this:
So how to get that special README on your GitHub profile?
Remember that special repository you needed to make to get your portfolio page at your_github_username.github.io. Yes, the repository with your username. Now, this repository if now is public and has a README.MD can use that README file to create that special introduction README.
But as I did not have that repository, so I went to create a new one and was greeted with this message:
And now, make your README as you wish and create a nice intro.
To take reference from my README file check out my repository
Special Note: I have used shields.io for the badges on the top of my introductory README.