Who can explain about character sets in fonts?

Question

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In general, there are such characters:
Cyrillic Extended (cyrillic-ext) Cyrillic, it seems like
Latin (latin) is needed Latin characters,
Greek Extended (greek-ext) Greek characters are also useful , it is not needed
Greek (greek) The same, not needed.
Vietnamese (vietnamese) Vietnamese, what the hell are needed.
Latin Extended (latin-ext) Latin
Cyrillic again (cyrillic) Cyrillic again.
What should I choose for Russian fonts?
What is for transliteration.
And I didn’t really understand, but it seems that there are fonts for numbers, etc., .correct if I’m wrong.
Previously, somehow it didn’t come to this) But now it’s time to learn)

Answer 1

For Russian Cyrillic

Answer 2

I also became interested in the difference between extended and regular fonts. For example, I took the PT Serif Cyrillic and PT Serif Cyrillic Extended fonts that I use in some of my projects and opened them in FontCreator to see the difference in the character set.
In the usual one, there were 329 characters, in the extended one, 464. The main difference between them is the additional letters of Serbian, Kazakh, Ukrainian and other languages. Otherwise, they are identical, except for the presence of the hryvnia sign in the extended version.
The regular version of the font is suitable for most sites in the Russian segment. Connecting the extended version makes sense only if the site is multilingual, that is, other languages ​​are used in addition to Russian and English.
This information is valid for the PT Serif font, in other fonts the character set may differ, although I don’t think it’s drastically.
Character set screenshots:
PT Serif Cyrillic
PT Serif Cyrillic Extended

Answer 3

In Extended there are characters for all sorts of rare Cyrillic alphabets (of which there are many developed for the natives of Siberia, the Far East and other post-Soviet space). Also there are Church Slavonic and simply outdated letters, there may be a set of superscripts. For an ordinary modern Russian text, Cyrillic is more than enough. And not only for Russian, but also for Ukrainian, Belarusian, Kazakh, Serbian and some others.

Answer 4

if you don’t need to write anything other than plain text, then it’s enough without extended, and if you need to display all sorts of circles (for example, in lists), different characters, then it’s better to choose extended