They aren't that useful.
First you need to start the game with the debug console enabled (google it).
d_query - search for a partial name of an item / mob / npc and get its ID in return
d_querynpc - type an npc id and get back its coordinates (if its already in the autopath database)
d_queryservice - forget
d_querymodel - Type in a partial model path and it spits out the items that use it
d_queryskill - forget
In general if these things are important to you you are already savvy enough to find that information on your own.