What exactly do the three "special locales" called "en_US_POSIX", "en_001" and "en_150" mean?

Question

There are quite a few English-language locales on my computer system (Windows 10). Most of them look like this, and make sense:

en_CA
en_DE
en_GB
en_IL
en_PK
en_US
...

But there are three special ones, which don't seem to correspond to a clear physical area:

en_001
en_150
en_US_POSIX

By doing some digging, I have extracted out the following "display names" for them (in order):

World
Europe
United States

Okay, so "001" means "World", "150" means "Europe" and "US_POSIX" means "United States", just as "en_US" already does?

What is the point of the duplicate "en_US" locales, and what is "World" and "Europe"?

It should be noted that numbers seem to be formatted just like in the US variants for both "World" and "Europe", which is unexpected. I thought they were gonna be using spaces for thousands delimiters, as I thought was considered the "international" standard, but they use commas, just like in the USA/UK:

123,456,789

Answer 1

You may find all this information in the webpage ICU Locale “English” (en).

You would fine there that en_US_POSIX is called "American English" and implies all sort of specific American settings as regarding dates, numbers, currency and much more.

en_001 has only some slight changes from en_US_POSIX.

As regarding the use of commas, just remember that this was decided by American developers from an American company named Microsoft.