With fail2ban, what is a ‘jail’?

 A Fail2Ban jail is a combination of a filter and one or several actions. A filter defines a regular expression that matches a pattern corresponding to a failed login attempt or another suspicious activity. Actions define commands that are executed when the filter catches an abusive IP address. A jail can have active or inactive status1 References: 1: Fail2Ban Jails Management | Plesk Obsidian documentation