dan@raspberrypi:~ $ pihole
Usage: pihole [options]
Example: 'pihole -w -h'
Add '-h' after specific commands for more information on usage
Whitelist/Blacklist Options:
-w, whitelist Whitelist domain(s)
-b, blacklist Blacklist domain(s)
--regex, regex Regex blacklist domains(s)
--white-regex Regex whitelist domains(s)
--wild, wildcard Wildcard blacklist domain(s)
--white-wild Wildcard whitelist domain(s)
Add '-h' for more info on whitelist/blacklist usage
Debugging Options:
-d, debug Start a debugging session
Add '-a' to automatically upload the log to tricorder.pi-hole.net
-f, flush Flush the Pi-hole log
-r, reconfigure Reconfigure or Repair Pi-hole subsystems
-t, tail View the live output of the Pi-hole log
Or man pihole to see the documentation on the Pi-hole itself, or, as Bucking_Horn pointed out:
How do I determine what domain an ad is coming from? - FAQs - Pi-hole Userspace
Or my personal favorite, run pihole -t and see what it does.