I mean like this: http://shells.red-pill.eu/
Can anyone explain how this works? I hope my post is not spam. I think its related to linux. Thank you

Having a shell account (as per your link) basically means that you are a user on a remote UNIX/Linux/BSD-type system.

https://en.wikipedia.org/wiki/Shell_account
http://www.egghelp.org/shell_using.htm
http://net.gurus.org/shell/?FRAME=yes&BODY=yes
http://support.suso.com/supki/What_I..._I_Do_In_It%3F

postcd, I wouldn't even go there. To me that is PURE SPAM. Linux is not something one should buy time or space for from the internet, or via monthly subscriptions. If you want to try Linux, there are LiveCD distributions where you can run from CD or a USB drive.

To add to my criticism, but also to be fair; I visited that link and some of the advertised links on it. The first one or two are "conditional", meaning you have to 'contribute' - whatever that implies, and the other one, you have to have "an invite code". Not real "free, and friendly". Further down you click on another link and it brings you to the old "Buy this domain name now" type of link. I see stuff like that and it raises my wariness antenna like crazy.