Ukrainian, Russian and in general almost all the other languages of the formers USSR Republics, use Cyrillic characters at the place of the most common Latin ones.
Those characters are not completely identical for every language, in fact every language has its own Cyrillic alphabet.
Speaking about Cyrillic, is very popular to hear this word: “transliteration”
In our case, the transliteration is a way for to “convert” the Cyrillic letters in Latin ones.
This procedure is made following a specific transliteration system which vary from language to language.
Now lets see more in detail about our two languages:
Ukrainian and Russian
The Russian and Ukrainian alphabets are very similar but not identical; there are several characters, 5 in Ukrainian and 4 in Russian which are not shared by these two languages:
Ґ, І, Ї, Є, ‘ are Ukrainian and not present in the Russian alphabet.
Ы, Э, Ё, Ъ are Russian and don’t exist in Ukrainian.
And even if many other letters are identical, they may have a different pronunciation:
In both alphabet is present the letter “И” but with a different sound.
the Russian letter “И” is the equivalent of the Ukrainian letter “І”.
the Ukrainian letter “И” is the equivalent of the Russian letter “Ы”.
In fact the letter “И” in Russian is transliterated as the Latin letter “I” and in Ukrainian as “Y”.
One more point is the differences between transliteration systems:
It is possible to see the Russian letter “Я” transliterated as “Ya” or “Ja”, the same happen with many other letters, the reason is the multiplicity of transliteration systems.
With the Ukrainian language can happen the same but there is a difference, exist an Official transliteration system, adopted by the Ukrainian Legal Terminology Commission, which should be the standard for the Ukrainian language.
For to know more about Russian transliteration systems: