I don't know what life is, but I do hope that quickly after death we will each find out.
An answer you can find in old movies [for example, "Heaven Can Wait" or "The Horn Blows at Midnight"] is that after life you are on a cloud, in a long line, waiting for Angel Gabriel to let you in the gate – or not.
Another possiblity is that you are deleted. There is less than nothing after life; you are as much not around as the memory you don't have of yourself before you were born.
It can be that you pass through the Bardo, a spooky old place, dream-like and filled with potential terrors, on your way to a next birth, as a human or some other sentient being on this or some other planet or somewhere or somehow in some other universe that you could never imagine. And it can be, that your reborn self comes tagged with lessons that you need to learn from all your prior lives, bringing you pains and pleasures that you deserve.
Many of us Buddhists pull out text from some sutra and say that Buddha told us not to speculate on those things be cannot know. And what might happen to us after death is just the kind of time-wasting speculation he was talking about. But Buddha also told us to use our own judgment of what we should think or do, and I think that considering the possibilities of what death might mean is a good use of a modest chunk of our life's time.
My hope is that we find out that a life is just a crazy old roller coaster ride.
At the end of life, you find yourself in a roller-coaster car, passing out of a dark tunnel. The track takes you up and down a few modest bumps, splashing through water, then your car is brought to a halt. You then remember before you were born when you embarked on the ride. And unless you had a remarkable life, in an instant you see how silly you were in life, misjudging what was important and what was unimportant.
Just as with roller coasters in amusement parks throughout the world, there is no lesson to be learned from a ride, and you disembark at the same place where you got on. Life, it turns out, is just a stunning experience, playing with that magical substance Ignorance. We are all of us, really, this single great Cosmic Self, frozen with absolute knowledge of everything and thus incapable of laughter, love, terror or hope. It is only through Ignorance that Cosmic Self can have adventures and experience the myriad feelings that Ignorance makes possible.
While life isn't a land of lessons, we do learn things about it: It turns out that chasing after money and status is not only life's biggest time waster, it is as destructive as living a life of crime. There is nothing that one can achieve by being well off financially and being respected by others. Indeed, by taking more than your share of earth's bounty and putting yourself above others, you add to the collective pool of misery. It is only from a deeply-felt compassion for others, and having modest possessions, that a life is profoundly satisfying.
But life is not a lesson. And whether we live as a seriel killer or an ego-free saint, there are no rewards nor punishments to receive or endure after life's end. There is only this: Certain knowledge about everything, and the opportunity to ride again.
Funny thing -- or, I should say, seriously, that it is not so funny a thing -- the Roller-coaster Theory does not pick up much religious support. I think the reason for this is that religions thrive when obedience to the religion is rewarded with prizes and benefits after death. The Twin Towers suicide terrorists each had twenty submissive virgins waiting for them after their murderous crashes. Good Christians have an eternity in Heaven. Well-behaved Hindus and Buddhists have karmic rewards, which might include a next life graced with prosperity, health, and attractive physical features. And, of course, for Buddhists there is Paranirvana, an absolute end to all suffering.
The Roller-coaster Theory comes then with marketting problems. The afterlife of the major religions promise a Parential [usually, Fatherly] Approval, and with it, happiness and security. So, there is a reason for us to be Good; our life has meaning. Be Good to make the Great Cosmic Dad proud.
In the Roller-coaster Theory, you are not still a child -- one of God's children -- you are a grown-up. And while dangers and terrors and random acts of violence are for the most part outside what you can control or influence, there is no one more in charge than you are. Your life can go wonderfully or horribly, despite your will, effort and talents; there is no guardian angel to guide or protect you. And so it is hard to feel that there is ultimately any meaning to being alive.
Why be good if there is no eventual reward? At the first level of understanding, it is because you can only really be good if there is no reward. At the second level of understanding – which trumps the first, obliterating it – we should be good for its own sake: Good for Goodness' sake. That's all. There's nothing else.
But what is Good? And what is Goodness' sake? There is no one outside yourself to tell you. As our heart/mind matures, the ideal of good becomes less treacly and rule-bound. We do the right thing outside the call of reasons for what feels like [and is] a growing abundance of wisdom and compassion.