When an application is open, it sends messages between the application, the operating system, and its components. This information is stored in log files. The operating system also creates logs and archives them during computer maintenance operations. When an application does not respond, the details are saved in a diagnostic report that you can use to diagnose the issue or that you can send to the developer (if asked to do so).
In the Maintenance pane, select the "Log messages and reports" checkbox, then click the Options button to access advanced settings.
Application logs: This option deletes the applications Logs.
Shells logs and restored sessions: You can delete the log that contains the list of commands entered and the restored sessions in Terminal using this option.
System archived logs: When the periodic scripts (daily, weekly, and monthly) are run, log files are archived and compressed. There can be up to seven archives per log. You can use this option to remove all of the compressed archives and some logs that the operating system saved.
Diagnostic reports: You can use this option to delete all user diagnostic reports, any diagnostic and crash reports created by the operating system, and to relaunch the syslogd daemon (a process that records the activities of the operating system).