Site groups, sites and endpoints
What you watch is arranged in layers. A site group is a named set of sites, and it belongs to you or to your organization. A site group can be moved to another workspace. A site is one website in a group: a name and its base address. An endpoint is one address on a site to check, with the status you expect it to answer and how often to check it.
Description
Every check is kept, with when it ran and the status it got, how long it took and whether it passed. That history is what Dashboards and the status site show. A group, a site and an endpoint each have an address of their own, so a link can take someone straight to a group, to a site in it, or to one endpoint's history.
Tech Detail
The stack of Dashboards and monitoring