What's in the deleted users folder?

The best way to migrate your useraccount
Is to create your account on the new machine with exact same username.

Then on the old mac open terminal and write down:

Code:

shopt -s dotglob

To be able to get all files incl hidden etc.
Then :

Code:

sudo rsync -ardv /Users/<your userfolder> <path to external drive or something>

This way you got a full backup of your account including email, application settings etc etc (no applications from /Applications folder tho)

Now on the new mac, make sure the userfolder is named the same

Also do the shopt and then rsync from externaldrive/userfolder to /Users

And you got all your files and settings on the new mac.

Your deleted users folder contains all data and settings from a useraccount you have deleted in the past where you have choosen to keep an image from. (The same as you make a backup like mentioned above)