kusura bakma means, if we directly translate it, "don't see/look at the deficiency/defect". by using the phrase, we mean "ignore the deficiency". in daily language, we use kusura bakma, to ask people to excuse us. it is a way of saying you are sorry. but you cannot say "kusura bakma" in every condition you use "excuse me" in English. for example if you are going to ask what the time is to a person passing by whom you don't know, in English you'd say "excuse me, what is the time please?" But in Turkish, you cannot say "kusura bakma, saat kaç lütfen?" this would not be correct.
with peace,