there are several definitions of "otaku"
1) polite(correct) way of saying house
2) many
people mistake the actual definiton of otaku when it comes to things such as "anime otaku" or "game otaku"
it used to be a insult but recently, the
definition has changed to a more positive meaning, although the word can still be used as a insult, it is more commonly used as a compliment
Ex. anata wa computer otaku desu ne (your a computer otaku)
although it is unclear as to when the
definition switched, many believe that it may have happened with popularity of animes and mangas going up