Linux is a popular platform for servers, when most people hear about Linux for the first time, they hear about Red Hat, and aside from the few people who think that Red Hat might be a club for women of a certain age, a lot of people who are new to Linux want to know what Red Hat really is.
Well, the thing is that, Red Hat is actually two things. Red Hat is a company and it is an operating system.
If you know a little bit about Linux, then you know that its operating system comes in different distributions, also sometimes called flavors, of Linux, each of these operating systems brings a little bit something different to the party, with a different set of features and a different perspective on what is and is not important in an operating system. Each of these flavors builds off of the Linux system kernel that is credited to Linus Torvalds.
When most people in IT talk about Red Hat, the software, they are talking about Red Hat Enterprise Linux, a commercial version of Linux that was developed for use primarily on servers, but can be also be used on individual workstations as well, there are many different versions of the system that can be scaled up or down based on the needs of the company and the existing systems and hardware that are already in place.
Red Hat the company is a technology company that does not actually sell the Red Hat operating system. No one sells the Red Hat System, it is considered Open Source software and is available at no cost. What Red Hat the company sells is the support and instillation services to support the Red Hat systems, both the hardware and software aspects. The company also provides its clients with easy access to the upgrades to the operating system, which come out every 18 to 24 months.
In case you are not familiar with the term 'Open Source', this refers to a piece of software that has its source code fully exposed and available to the public. This source code can be altered by anyone at any time. People who have the software are even free to re-distribute their modified software and make it available either at no cost or at a profit, provided that they also leave the source code exposed for the free modification of others. This is sometimes called free software, but free does not refer to the costs, but to the free and open access to the software's code.
Overall, Red Hat is the most popular distribution of the Linux operating system for servers, but there are a wide variety of different operating systems for Linux, you can find out more about Red Hat at the Red Hat site or more about the Linux community on the Linux site (http://www.linux.org/). Other popular versions of Linux include Ubuntu and Mandriva, which you may have heard of referred to as Mandrake.