"Transliteration" refers to the rendering of non-roman scripts in roman characters. This is different from transcription -- transcription concerns the sounds letters make, while transliteration concerns the letters themselves.
A few searching strategies that you are probably familiar with will come in handy when using Orbis, especially to search for materials in Slavic languages.
To search for a full phrase in a keyword search, put it in quotes. (EX: "Time of Troubles")
To look for variant forms of a word, use * or ? where necessary (EX: bolshevi? or bolshevi* will yield results for bolshevik, bolsheviks, bolsheviki, bolshevist, etc.) This is especially helpful for finding variants forms of Slavic nouns, verbs, and adjectives in the catalog.
Always attempt a transliterated search first. Cyrillic script is not yet included in all of the records in the library catalog.
The standard for libraries is the Library of Congress transliteration system. The tables below illustrate transliteration systems for non-roman languages you'll find within Yale's libraries as well as others.