what is actually dying when we die?

Ah, what a grand question. Terrifying, unanswerable, not worth thinking about? Not sure. My views on the subject continue to evolve but for the moment I would classify them as the belief in infinite possibilty. That is, when one dies, it is only the end of the physical body and it's capability to function. Everything and anything else is possible. Maybe the grand finale is merely a transfer/explosion/reformation of our enegry/soul/being. 

This poem was written in 1932 by a Mary Elizabeth Frye and I think it's beautiful 

Do not stand at my grave and weep,

I am not there; I do not sleep.

I am a thousand winds that blow,

I am the diamond glints on snow,

I am the sun on ripened grain,

I am the gentle autumn rain.

When you awaken in the morning’s hush

I am the swift uplifting rush

Of quiet birds in circling flight.

I am the soft star-shine at night.

Do not stand at my grave and cry,

I am not there; I did not die.