Alice

What really are dreams?

Nik, the protagonist has always been a lucid dreamer.
However since he was young, Alice would always show up in his dreams.
She seems to be in full control of his dreams, and knows exactly when he's about to wake up.
Until one day, He wakes up only to find himself crying...
"Am i... crying?
Her name...
What was it?"

Who really is Alice? Why is she always showing up in his dreams?