Linux and Unix operating systems comes in a wide range of flavors often bundled as different distributions by different vendors. Every one of these distribution also comes with an often pre-defined and latest version of the Linux kernel. Sometimes you need to know the exact name and version of your operating system, machine as well as the kernel, be it to install the correct version of a software, find if a hardware is compatible or be it to upgrade your OS itself. There are several ways to check your operating system and linux kernel versions. As each distribution (or distros) are slightly different some of the commands might work in some distros while some maynot.
uname
is the linux command which prints out the name, versions and other details of the machine and kernel running on the machine. It is basically short for Unix Name. This is usually part of the core-utils package and should be available on almost all distros. There are several options available to print out just the kernel detail