'Accent' is the pronunciation of the sounds (phonetics) , plus other phonological features such as stress, intonation and 'voice quality'. It is basically the way you sound when you're speaking. Everybody has an accent of some kind.
'Dialect' is non-standard grammar and vocabulary. It's the words, structures and expressions which are particular to a place where people live. Arabic is a language, and there are many different dialects of Arabic which are spoken in different countries and different regions.