In the early 90s, the GNU Project had put together the whole system, except for the kernel.
The GNU Project had started a kernel, GNU Hurd, but developing it was harder than expected.
Thankfully, they didn't need to wait for the Hurd, because a kernel named Linux was freed in 1992, which fit into the last major gap in the GNU system. However, making them work together was not a trivial job.
Together, the system is named GNU/Linux.
Today, there are many different variants of GNU/Linux.
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