I want know user api settings how to work

login brower block.org and open settings–>> api settings. now I dont know the api settings how to work,
Let me know if anyone knows,please

I read the faq about what is blockstack from blockstack.org. that has a explain: "The applications on blockstack are server-less and decentralized. Developers start by building a single-page application in Javascript, Then, instead of plugging the frontend into a centralized API, they plug into an API run by the user. "
I think Is there a connection between settings – >> api settings and API run by the user.
Anybody? Tell me, please