نعم and ايوة both means yes but the first one which is نعم is YES in standard arabic ( الفصحى ) while ايوة YES in slang arabic ( العامية ) both are usable hope its useful

(1) نـعـم Na'am : is a Classical Arabic word that means ''Yes'' or ''Alright''. (2) أيـوة Aywa: is a Masry (Egyptian Arabic) word of Coptic origin and means ''Yes''. Aywa is used allover Egypt and even passed to surrounding countries thanks to the widespread Egyptian movie industry, but it's simply an Ancient Egyptian word.

نعم = yes in standard Arabic ايوه = yes in slang and it differs from one Arabic country to another