Many hosting providers claim to provide optimal uptime for their customers. What is uptime, though?
Uptime is simply the length of time a server, website, etc. is on and operating properly. In simpler terms, if your server is frequently inaccessible and takes your website down, then it has a lot of downtime, or low uptime. Good uptime therefore means that your server simply does not lock up or go offline often, or at all, and your website is available to your visitors at all times.
Website availability, website uptime or uptime are often times used interchangeably. A website with high uptime rate guarantees consistent delivery of intended services, while a website with low uptime rate introduces doubt to its users.