Uptime

Uptime refers to the amount of time a server is up and running. Interruptions to service (i.e., when your website is unavailable) are known as downtime. When looking for a hosting provider, you’ll see that they mention 99.9% uptime a lot.
Some offer uptime guarantees, too. This means that if their uptime falls below a certain level (usually 99.9%), they’ll give you credit for the additional downtime as a form of compensation. Look for the hosting companies with the highest levels of uptime: you want your website to be available when visitors come by.