What is the diffrence between nusach Ashkenaz, Ari, and Sefard. Where can I find a detailed explanations on this subject?
There are many minor differences between nusach Ashkenaz and the nusach used by Jews from Moslem countries- Yotzei Sfarad. It is simple to discover these just by comparing the siddurim. There is a difference of opinion as to what is "nusach HaAri"-Chabad calls its siddur nusach HaAri, while HaRav Ovadia Yosef writes in Shu"t Yabiya Omer that the nusach used by Yotzei Sfarad is the nusach that was used by the Ari. What is called today nusach "Sfard" is a nusach that was adopted by Chassidim who incorporated into nusach Ashkenaz some of the nusach of Yotzei Sfarad.