Isekai (異世界) is a Japanese word that roughly translates to "another world". It is a genre predominantly characterised by one or more people being transported or reincarnated into another world.
PubNIX is short for Public-access UNIX. In this case, UNIX refers to any system modelled after the original UNIX operating system, such as the BSDs or Linux; this server runs on Debian Linux. PubNIXes are shared remote computers that users can connect to from home. They offer free and collaborative ways to learn how to use UNIX-like systems from the command-line.
Currently, this is the only way to host your own content on isekai.rocks.