Debian is an operating system which is set of basic programs as well as utilities that make our computer run. At the center of an operating system is the kernel. The kernel is the basic program on the computer which performs all inside work and enables you start programs.
The most important thing is that it is a free operating system. Linus Kernel and OS tools from GNU project, both are used in it, that is why, it is also called debian GNU/Linux or debian linux.
If we compare debian vs ubuntu, the only difference is with the installation. The restraint of the Ubuntu installer is that it provides slight lesser user control over the process. If you are having trouble installing, or want more control, Ubuntu directs you to its alternate CD. This alternate CD is simply a rebranded version of the Debian Installer. Contrary to what you may have heard, the Debian Installer is not particularly hard to use. Infact, its raphical version lacks polish. Setting up debian server is very easy and normal installation will support for server setup. A Debian Live system boots from removable media, without requiring installation or previous configuration. Debian mirrors website has excellent bandwidth and available round the clock 24/7.