Someone has already explained the use of this particle, but since I can't find the relevant post, here is what Wikipedia says about it:
يَا • (yā)
vocative particle preceding a noun used in direct address; only rarely omitted in such contexts; occasionally translated as o or hey يا كندا! yā kanadā! O Canada! يا كريم... yā karīm... (Hey) Kareem, ... يا حبيبي! yā ḥabībī Hey my love!