Linux is Just a Kernel: What Does it Mean
Well, technically, Linux is just a kernel, not an operating system. However, the term Linux is often referred to a complete operating system that includes a shell (like bash) and command line and/or GUI tools to control the system. The technically correct term for this complete operating system is Linux distribution or simply Linux distro. Examples of popular Linux distributions include Ubuntu, Red Hat, and Debian.
Back in 1991, what Linus Torvalds created was the kernel only. Even today, he works on the Linux kernel. He doesn't code anymore but supervises which code goes into the kernel.