Due to one of the main features of Unix base operating systems licences, these OSs can be developed and distributed by anyone. So this manner caused many companies and many individuals developed the Linux in order to create a new distribution with special specifications for general or specific usage.
Through various websites within internet, you can find various websites providing information about different distributions and how you can have one, though there are few websites which can be considered as reference and the on I always use is DistroWatch.com. This site provides all the basic information you need for picking up a specific distro to fit your needs. Perhaps you may need an OS for running a webserver, or you might want to have one on your personal computer or laptop for daily usage, or maybe you want to have an individual OS for a firewall.
The only missing feature in this website is the lack of categories, so you can not compare different OSs in the same category.
To sum-up, this is the website I always use as reference and I recommend you to check this website out to see how much this can be useful and it’s free of charge 😉 .