Alerting
In plain terms
Notifying responders when metrics cross thresholds.
Going deeper
Alerting triggers notifications when monitored conditions indicate problems, so teams can respond before users are badly affected. It turns monitoring into action.
Under the hood
Good alerts are actionable and tied to symptoms; poor thresholds cause fatigue or missed incidents.
Examples
Prometheus Alertmanager, PagerDuty, threshold alerts, SLO alerts, on-call.
Think of it like...
Like a smoke alarm that sounds only when there's real danger worth acting on.