What Verifying actually does?

[Miroslav Suchý]

When installing package I will get:
   Installing : zsh-5.0.7-1.fc21.x86_64 
                        1/1
   Verifying  : zsh-5.0.7-1.fc21.x86_64 
                        1/1

What actually Verifying does? Is it the same as -V? Why it is in transaction? I tried to search for documentation of 
this step, but found nothing.

-- 
Miroslav Suchy, RHCE, RHCDS
Red Hat, Senior Software Engineer, #brno, #devexp, #fedora-buildsys