I have no idea what death means to the dead. Yes, yes - whole religions are based on people's beliefs regarding this very subject, but that doesn't mean anyone actually knows what happens. All the theories amount to leaps of faith - belief without corroborating evidence. I happen to believe that we all emerge from a pool of whatever you want to call the essence of life, and that when we die we go back to that pool. And I submit that my expertise in this area matches that of every (living) religious theoretician in the world, since our experience of it is precisely the same.
So, when I speak of the afterlife, I mean my life after somebody close to me dies.
Put in theoretical terms, it sucks. You never stop missing them. The best you can hope for is to get used to missing them. It helps to remember good things about them, especially things that make you laugh; but, frankly, there will be moments even years later when something reminds you of them, and you just ache to see them again.
The bright side of all this is that your memories keep them alive in some small way. Although my friend Wayne has been dead nearly eight years now, I still remember the last joke he told me. (Referring to his cancer diagnosis, he said, "Nobody in my family has ever had cancer, as far back as I've been able to trace the family tree. You know what this means, don't you? It's just as I feared - I'm adopted, and those bastards never told me!") Since my mother's death nearly two years ago, I have become hypersensitive to birds and flowers. It's as if she's in my head somewhere, using my eyes to catch glimpses of her favorite things.
The upshot is that it's important to share good things with the people you love - make good memories, include a solid dose of silliness, and laugh as often and as hard as you can. All that stuff will be important some day for carrying survivors through the afterlife.