This option will display the list of Domain Controllers in the forest, and which sites that DCs are allocated.  Additional information is also provided, the default context for the DC, the FSMO roles installed, dns hostname, and IP address, if the Perform DC DNS resolution option is selected.

The FSMO Roles uses the following abbreviations:

G - Global Catalog
D - Domain Master
I - Infrastructure Master
P - PDC Master
R - RID Master
S - Schema Master