السلام عليكم ورحمة الله
Jazaa= reward (Jaza
K the K here refers to you (Male))
In Quran It could mean to be rewarded for your good deeds, OR panished for your bad deeds.
Khair (Khairan: The (an) is for when you continue talking non-stop )= good or goodness
the whole word means (May Allah reward you for the good or good things...)
Hope this clears it..