Could someone explain them to me? Local, Cloud, etc. I'm a very confused about what they are and how they are used.
In what context? Rule Machine? If so, you can use an "endpoint" as a trigger for the rule. Cloud will work from the internet, while local needs access to your LAN. Either is something you can use to supplement or replace a traditional trigger. An HTTP GET is how you can use the endpoint, which just accessing the URL in web browser would do (among other options).
If you're developing a custom app, similar ideas exist, but you need Oauth enabled and have to define the endpoint(s) and assign meaning to them somehow.
I had noticed that you can use a cloud endpoint as a trigger. What about it is the trigger? Seems like it's just a web address.
Hitting the URL with an HTTP GET is the trigger. This is the "easiest" HTTP 'method to hit--just typing the address in a web browser's URL bar and hitting Enter will do the trick (like you're trying to navigate to a web page, though you won't see anything come back). However, some third-party integrations you might use probably also have ways to do a GET, as does Rule Machine itself (say, from another hub), and those ways are generally how you'd actually use those to make automations.
I use endpoint triggers to open and close my garage doors with Siri. You create a Siri shortcut that opens the endpoint trigger in a browser this triggers the rule that either opens or closes the garage door.
This makes sense. Gives me a better understanding of the concept.
Is there any way to use the cloud endpoint with a request other than HTTP GET? I have several Reolink cameras, and they don't integrate well. But I can set them to request an ftp transfer on motion detection. I'm trying to figure out if I can use that as a trigger. Any thoughts or hints?