Linux is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on 1991.09.17 by Linux Torvalds. Linux is typically packaged in a Linux distribution.
Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project.
To find out which Linux distribution is running on your machine, you can use
$ hostnamectl Static hostname: ip-172-31-24-17 Icon name: computer-vm Chassis: vm Machine ID: b54d0220fe634fa4a96fa3d0641ab3ea Boot ID: 5208456664c54b09b34be6b541fa7588 Virtualization: xen Operating System: Ubuntu 20.04.1 LTS Kernel: Linux 5.4.0-1029-aws Architecture: x86-64
More specifically, to find out the Kernel version, you can use
$ uname -r 5.4.0-1029-aws