Hi Mr Bok! Apache is the Web Server application used by Linux. So you are viewing a Linux Web Server rather than the Microsoft one. Why they named it Apache? You may want to browse here: http://www.apache.org/
Apache is a web server (www.apache.org) that can run on pretty much anything (since you can compile the source code onto pretty much anything - including Windows). Administrators of Windows servers would be wise to get rid of IIS and install Apache instead, since it doesn't bend over and take it from every bit of malicious code on the planet.