Gadling teaches you to read the Cyrillic alphabet in 5 minutes mentions that there's some letters in Cyrillic that look like letters in the English alphabet, but their pronunciation in Russian is different to the similar looking letter in English:
3. Some letters ... look familiar but don’t sound like their English counterparts. The Russian letter “H” makes the “N” sound, “y” makes the English “oo” sound, and “B” sounds like the English “V.” This letter, И, which looks like a backwards “N”, makes the “short i” sound, as in the English word “pin.” The Russian letter “Я” sounds nothing like [its] mirror image in English. Instead, it makes a “ya” sound, as in “yacht.”
Why is this the case?
I tried looking it up, but only found sites with user generated content discussing the issue.