[1]https://tfl.gov.uk/info-for/taxis-and-private-hire/licensing...
In New York City, cabs that have medallions for street hails are referred to colloquially as "yellow cabs" and those which do not are referred to as "black cabs" (more properly: "livery cab"). Both yellow cabs and black cabs are regulated by the TLC, but black cabs are not allowed to pick people up off the street. Instead, you have to call the company to arrange a pickup (using a mobile app qualifies as "calling" for this purpose).
Uber, Lyft, Juno, etc. are all regulated in New York City as black cab services, which means they can't take street hails, but they operate otherwise identically to all other non-medallion black cab services, with TLC-licensed drivers.
The 'green badge' is your licence. There's green, yellow, and 'minicab' licences. Green is a citywide black cab, Yellow is constrained to one area, and minicab is no black cab, but dispatch-only.
'The Knowledge' is the test (and associated training) required to become a black cab driver. It's years worth of study. It's pretty much memorising an A-Z, but also knowing the best routes, at different times of the day, etc.
Three vehicles you can expect to see almost everywhere in London are red busses, black cabs, and scooters with a clipboard on the handlebars. The latter are drivers on their multi-year study of The Knowledge.
https://www.nytimes.com/2014/11/10/t-magazine/london-taxi-te...
There's a 1996 documentary on the process that's pretty interesting - https://www.youtube.com/watch?v=yvFKh_3evC8
Separately, this is the kind of non robots doing manufacturing automation that I think it's important to think about when we have discussions of future work, etc.
Because on the one hand it's stunningly fantastic that what used to take someone 4 years and a series of examinations to achieve is now included for a negligible cost in the pocket supercomputer (of 1996) that we all carry around in our pocket. But, it's also a huge shift for all these industries.
[1] https://en.wikipedia.org/wiki/Taxicabs_of_the_United_Kingdom...
It's a drama rather than a documentary, but highly recommended (IMO).
I was browsing the /r/London subreddit so assumed too much context for a global forum