What's Mixing?

Listening to the whole piece and understanding how it fits together.
Trying to grasp the essence of the song - what is its story, its mood, its emotional flavour - in consultation with the people who made it.
Working on what sort of listening space suits that essence - intimate? Spacey? Airy? A hot, packed club? A concert hall?
Carefully using reverbs to help create that listening space.
Listening to each instrument and voice carefully and working out how they can fit together comfortably into a whole picture
Using EQ to shape tone, compression to shape the dynamics of each part, and other effects and processing to enhance and perhaps dramatise.
Balancing volumes and place in the stereo image.
Automating volumes and effects, to add drama or emphasis at different points, or to help transitions from one song section to another.
Listening to the whole song after these processes and applying any treatments necessary to make the whole mix ‘glue together’.
Fading out, or enhancing the ending.