Raspbian [1] is the name of the original community project to port Debian to armhf (armv6 hard float) which ran on the Raspberry Pi 1.
Raspberry Pi put our their own images based on this, and called it Raspbian until about 2020 [2] when they started calling it "Raspberry Pi OS" after they started producing aarch64 images.
This reminds me of a part I didn't mention in the article - they initially actually set up a second company called "Shady Apps" with a separate Developer account from which they upload the "people will buy anything for 99p" apps, on the basis that they would keep the "App Start" one clean for just the better quality ones.
One day Alex showed me a bunch of such apps they'd made - the "orgasm button" was one I can recall...
In many ways it was a really good first job for me - the people and dodgy business ongoings aside - what I needed at the time was to build stuff in my own way on my own terms, but with purpose. The next job was a bit of a shock, but it was another new experience.
Raspberry Pi put our their own images based on this, and called it Raspbian until about 2020 [2] when they started calling it "Raspberry Pi OS" after they started producing aarch64 images.
[1] https://www.raspbian.org/
[2] https://www.raspberrypi.com/news/8gb-raspberry-pi-4-on-sale-...
Further reading:
[4] https://www.tomshardware.com/news/raspberry-pi-os-no-longer-...
[5] https://unix.stackexchange.com/a/602658/253655