CentOS is short for Community Enterprise Operating System. This is one of the leading Linux distributions for servers and it's well known as one of the most reliable and secure Operating Systems available. CentOS is open-source software, which means that you will be able to personalize it in any way you see fit, adding and removing packages or updating the code of all of them. It is also free to distribute and use, so you won't have to pay any license fees, which means that the total price that you'll have to pay for a server making use of CentOS will be more affordable than the price for a server working with another OS. What makes CentOS unique among various other Linux distributions is its huge developer society, which will help you discover the answer to any question or problem you might have. Furthermore, each version that is released officially is supported for 10 years, that is is a lot longer than with any other OS. This means regular security and stability updates which will provide a stable software environment for your web applications in the long run.