Transliteration is a conversion of a text from one writing system to another.[1][2] It swaps letters in predictable ways (such as α → a, д → d, χ → ch, ն → n or æ → ae). The word comes from the prefix trans- (in this case, referring to switching the letters around) + the Latin word littera (meaning "letter") + the suffix -ation (which makes the word into a noun that talks about the process of doing something).
Transliteration is not about the sounds of the original. It is about the type or written characters, mostly the letters.
For example, the name for Russia in Cyrillic script, "Россия", is usually transliterated as "Rossiya". So, 'сс' is transliterated as 'ss', but pronounced IPA: [s].
Transliteration typically goes grapheme to grapheme. Most transliteration systems are one-to-one, so a reader who knows the system can reconstruct the original spelling.
Transliteration is opposed to transcription, which maps the sounds of one language into a writing system.