Understanding the log

Hello,
 I'm reading the log and don't understand a lot of lines. Do you have documentation on the messages and the meaning?
Can somebody help me ?

Oct 3 19:04:34 charles-N240JU org.gtk.vfs.Daemon[9128]: ** (gvfsd:9201): WARNING **: dbus_mount_reply: Error from org.gtk.vfs.Mountable.mount(): L'obtention de la liste des partages du serveur a échoué : Connexion refusée
Oct 3 19:04:34 charles-N240JU org.gtk.vfs.Daemon[9128]: ** (process:10896): WARNING **: Couldn't create directory monitor on smb://x-gnome-default-workgroup/. Error: L'emplacement indiqué n'est pas monté
Oct 3 19:04:37 charles-N240JU org.gtk.vfs.Daemon[9128]: ** (gvfsd:9201): WARNING **: dbus_mount_reply: Error from org.gtk.vfs.Mountable.mount(): L'obtention de la liste des partages du serveur a échoué : Connexion refusée
Oct 3 19:04:37 charles-N240JU org.gtk.vfs.Daemon[9128]: ** (process:10890): WARNING **: Couldn't create directory monitor on smb://x-gnome-default-workgroup/. Error: L'emplacement indiqué n'est pas monté
Oct 3 19:14:01 charles-N240JU CRON[11026]: (root) CMD ( test -x /etc/cron.daily/popularity-contest && /etc/cron.daily/popularity-contest --crond)
Oct 3 19:14:01 charles-N240JU CRON[11025]: (CRON) info (No MTA installed, discarding output)
Oct 3 19:14:12 charles-N240JU gnome-session[9268]: Nautilus-Share-Message: Called "net usershare info" but it failed: L'exécution du processus fils « net » a échoué (Aucun fichier ou dossier de ce type)
Oct 3 19:16:36 charles-N240JU org.gnome.evolution.dataserver.Sources5[9128]: ** (evolution-source-registry:9361): WARNING **: secret_service_search_sync: must specify at least one attribute to match
Oct 3 19:17:01 charles-N240JU CRON[11084]: (root) CMD ( cd / && run-parts --report /etc/cron.hourly)
Oct 3 19:17:44 charles-N240JU gnome-session[9268]: gnome-session-binary[9268]: GLib-GObject-CRITICAL: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
Oct 3 19:17:44 charles-N240JU gnome-session[9268]: gnome-session-binary[9268]: GLib-GObject-CRITICAL: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
Oct 3 19:17:44 charles-N240JU gnome-session-binary[9268]: GLib-GObject-CRITICAL: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
Oct 3 19:17:44 charles-N240JU gnome-session-binary[9268]: GLib-GObject-CRITICAL: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
Oct 3 19:17:44 charles-N240JU gnome-session[9268]: gnome-session-binary[9268]: GLib-GObject-CRITICAL: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
Oct 3 19:17:44 charles-N240JU gnome-session-binary[9268]: GLib-GObject-CRITICAL: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
Oct 3 19:17:45 charles-N240JU gnome-session[9268]: gnome-session-binary[9268]: GLib-GObject-CRITICAL: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
Oct 3 19:17:45 charles-N240JU gnome-session-binary[9268]: GLib-GObject-CRITICAL: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
Oct 3 19:17:45 charles-N240JU gnome-session[9268]: gnome-session-binary[9268]: GLib-GObject-CRITICAL: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
Oct 3 19:17:45 charles-N240JU gnome-session-binary[9268]: GLib-GObject-CRITICAL: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
Oct 3 19:17:45 charles-N240JU gnome-session-binary[9268]: GLib-GObject-CRITICAL: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
Oct 3 19:17:45 charles-N240JU gnome-session[9268]: gnome-session-binary[9268]: GLib-GObject-CRITICAL: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
Oct 3 19:17:45 charles-N240JU systemd[1]: Stopping RealtimeKit Scheduling Policy Service...
Oct 3 19:17:45 charles-N240JU systemd[1]: Stopped target Timers.
Oct 3 19:17:45 charles-N240JU systemd[1]: Stopped Daily apt upgrade and clean activities.
Oct 3 19:17:45 charles-N240JU systemd[1]: Stopped Daily apt download activities.
Oct 3 19:17:45 charles-N240JU systemd[1]: Stopping Daemon for power management...
Oct 3 19:17:45 charles-N240JU systemd[1]: Stopping Session c2 of user charles.
Oct 3 19:17:45 charles-N240JU bluetoothd[947]: Terminating
Oct 3 19:17:45 charles-N240JU systemd[1]: Stopped Stop ureadahead data collection 45s after completed startup.
Oct 3 19:17:45 charles-N240JU systemd[1]: Stopping ACPI event daemon...
Oct 3 19:17:45 charles-N240JU systemd[1]: Stopped Timer to automatically fetch and run repair assertions.
Oct 3 19:17:45 charles-N240JU systemd[1]: Stopping Authenticate and Authorize Users to Run Privileged Tasks...
Oct 3 19:17:45 charles-N240JU systemd[1]: Stopping Manage, Install and Generate Color Profiles...
Oct 3 19:17:45 charles-N240JU systemd[1]: Stopping User Manager for UID 1000...
Oct 3 19:17:45 charles-N240JU systemd[1]: Closed Load/Save RF Kill Switch Status /dev/rfkill Watch.
Oct 3 19:17:45 charles-N240JU systemd[1]: Stopped Daily Cleanup of Temporary Directories.
Oct 3 19:17:45 charles-N240JU systemd[1]: Stopped Timer to automatically refresh installed snaps.
Oct 3 19:17:45 charles-N240JU systemd[1]: Stopped target Sound Card.
Oct 3 19:17:45 charles-N240JU systemd[1]: Stopped target Bluetooth.
Oct 3 19:17:45 charles-N240JU systemd[9005]: Reached target Shutdown.
Oct 3 19:17:45 charles-N240JU systemd[9005]: Starting Exit the Session...
Oct 3 19:17:45 charles-N240JU systemd[9005]: Stopped target Default.
Oct 3 19:17:45 charles-N240JU systemd[9005]: Stopped target Basic System.
Oct 3 19:17:45 charles-N240JU systemd[9005]: Stopped target Timers.
Oct 3 19:17:45 charles-N240JU systemd[9005]: Stopped target Sockets.
Oct 3 19:17:45 charles-N240JU systemd[9005]: Stopped target Paths.
Oct 3 19:17:45 charles-N240JU bluetoothd[947]: Endpoint unregistered: sender=:1.81 path=/MediaEndpoint/A2DPSource
Oct 3 19:17:45 charles-N240JU bluetoothd[947]: Endpoint unregistered: sender=:1.81 path=/MediaEndpoint/A2DPSink
Oct 3 19:17:45 charles-N240JU systemd[1]: Stopping Bluetooth service...
Oct 3 19:17:45 charles-N240JU systemd[1]: Stopping Disk Manager...
Oct 3 19:17:45 charles-N240JU thermald[729]: Terminating ...
Oct 3 19:17:45 charles-N240JU rsyslogd: [origin software="rsyslogd" swVersion="8.16.0" x-pid="731" x-info="http://www.rsyslog.com"] exiting on signal 15.