Uptime describes the period when a website (or content) is available and running as it should. It is measured in percentages. High availability represents 99.999% – which is a yearly downtime of fewer than 5.26 minutes.
Downtime is the opposite of uptime. When a website is down, it cannot perform its purpose or generate sales and creates a bad reputation with prospective or existing customers. The ability to act fast is essential.
Uptime monitoring ensures that you’re never oblivious to website downtime. It provides an overview of the availability of your website and alerts you should your website ever go down. This helps minimize the damage caused by downtime. 
By informing you immediately, getting your website back up and running can be achieved as quickly as possible, thereby reducing the number of customers turned away by a 400 or 500 error code.
