Hello Ahsoka,
Following files are created by either JUNOS or the underlying operating system (BSD):
aprobed
apsd
authd_sdb.log
chassisd
cosd
dcd
dfwc
dfwd
eccd
inventory
l2tpd
l2tpd_cfg
license
lmpd
mastership
messages
pf
pgmd
rdd
rtspd
sampled
smartd.trace
user
utmp
wtmp
The auto-complete of the command 'show log ?' gets the list of files from /var/log , where the default and user-created (via [system syslog file xx] or any 'traceoptions') are stored.
Cheers,
Erdem