What does the upgrade tool actually do?

[The Keeper]

What does it do besides of changing sources.list to point to the latest distro and running apt-get dist-upgrade?

[Pumalite]

It upgrades all the programs you have installed(which are not standard) and installs programs necessary for the new environment.

[The Keeper]

But that's what apt-get dist-upgrade does. What else besides that does the upgrade tool do?

To clarify my question: Ubuntu devs recommend to use the upgrade tool instead of dist-upgrade. Why? What else does it do?