Monitoring
Monitoring is the use of automated tools that watch your live site around the clock and alert someone the instant something goes wrong, such as when the site goes down, pages slow to a crawl, or errors start piling up.
The goal is to find out about problems before your visitors do. Without monitoring, you often learn that a site is down from an angry email, hours after it happened. With it, an alert reaches someone within minutes. Good monitoring watches uptime, page speed, and error rates, and it's a cornerstone of post-launch operations.