A systemd component called journald collects and manages journal entries from all parts of the system. This is basically log information from applications and the kernel.
1. To see all log entries, starting at the oldest entry
journalctl
2. journal entries from the current boot
journalctl -b
3. To see only kernel messages, such as those that are typically represented by dmesg
journalctl -k
To see the above only from the current boot
journalctl -k -b