journalctl is a command line utility in Linux used for viewing and managing the system log files, also known as "journals". These logs are stored in a binary format and provide a centralized location for storing system and application logs. With journalctl, you can filter, search, and manage system logs in real-time, as well as examine previous boot logs and system state. Additionally, you can use journalctl to troubleshoot system issues, monitor system performance, and keep track of system events.