unreal source in lense

I was having trouble while thinking about the unreal source for refreaction through a lense... In lense light is refracted twice...the real image for the first refraction works as an unreal source for the second refraction... I understand how it is... But fail to feel it...
I mean how would I see the unreal source as? I mean to say what is the diiference between real and unreal source... from a real source light really comes out,it seems to come from a unreal surce bu actually it doesn't... How would I know the difference between this two...

I know there's no difference to us for real and unreal image...

I think I am having a little discomfort to regard the source as unreal...