Let’s say I typed a module, and made a consistent mistake of spelling “automata” as “automiata”. I can use any editor to search for the pattern “automiata”. However, I may also use the word to begin a sentence, which means I also need to search for “Automiata”.
In Vi, I can use the search command /[Aa]utomiata to locate all occurances of the word. The [Aa] part means that the first letter can be either an uppercase ‘A’ or a lowercase ‘a’.