I am using pihole for some months now, used the dev version an now switched succesfully "back" to master 3.01.
Pi-hole is working very nice but if I go to settings - tail pihole-FTL.log, nothing happens. I never got any infos/logs in this menu section.
Using nano pihole-FL.log opens a big log file, but this is hard to read...
Anyone can help?
It's true, as @Mcat12 said, that it doesn't get written as often as pihole.log.
Here is some example output of pihole-FTL.log
[2017-05-08 00:00:04.217] Notice: Increasing domains struct size from 0 to 1000 (344.27 KB)
[2017-05-08 00:00:04.217] Notice: Increasing clients struct size from 0 to 10 (344.45 KB)
[2017-05-08 00:00:04.233] New client: 192.168.1.103 (0/10)
[2017-05-08 00:00:04.381] New client: 192.168.1.115 (1/10)
[2017-05-08 00:00:04.504] New client: 127.0.0.1 localhost (2/10)
[2017-05-08 00:00:05.843] Notice: Increasing overTime struct size from 100 to 200 (360.74 KB)
[2017-05-08 00:00:06.481] Reading from /var/log/pihole.log (rw-r--r--)
[2017-05-08 13:34:51.041] Notice: Increasing queries struct size from 10000 to 20000 (690.57 KB)
[2017-05-08 16:11:48.431] Notice: Increasing overTime struct size from 200 to 300 (694.58 KB)
[2017-05-08 21:03:04.039] Notice: Increasing domains struct size from 1000 to 2000 (718.39 KB)
So pihole.log is very busy since it logs every single query that happens on your network, but pihole-FTL.log shows more informational things that are happening. @DL6ER can give you some specifics, but hopefully that makes sense.
If you want to see some activity in the Tail pihole-FTL.log window I recommend you log in to your Pi and type
sudo service pihole-FTL restart
while the windows is open. The output is not very verbose (except when you have enabled debugging mode, which seems to be the case in @jacob.salmela's log excerpt).