Difference between apt-get upgrade and apt-get dist-upgrade

Imagine you have installed packages A-1.deb and B-1.deb A-1.deb depends on packages Adep1-1.deb and Adep2-1.deb while B-1.deb depends on package Bdep1-1.deb: A-1.deb | `—– Adep1-1.deb `—– Adep2-1.deb B-1.deb | `—— Bdep1-1.deb Now, there is a new package available for program A, namely A-2.deb. A-2.deb still depends on Adep1-1.deb but now it also depends on a