@chiscornell started following me on Twitter.com. I’d never heard of him. I clicked on the link to his web page from his bio. I listened to some of his music, I downloaded a couple of wallpaper photos of him, I followed him back. He invited his followers on Twitter to become fans of his on Facebook. I did that. He let us know when Amazon.com was having a sale on his new album, Scream. I bought the album. I like the music. I recommend it to friends.
That is how Twitter works.