This thread is about a community-created Web browser page that displays the information in your SmartThings account. Like your devices, your routines, etc.
It gets that information by using cloud access to the SmartThings API, an official feature.
Discussion of that official feature and “what it’s intended for” would be off topic here. So why don’t you start a new thread in the following section of the forum.? I’m sure people would be happy to go into the API details with you there.
But the shortest answer is that the API is a publicly available way of accessing a SmartThings account via the SmartThings cloud. (Look in the lower left of the cloud in the official schema.)
As far as modes, see the following FAQ. It’s old, but still valid.