Confusion between channels and channel triggers

I struggle to understand the difference between channels and channel triggers.

Take the astro binding for example:

There are channels and channel triggers. If I want to write a rule that is executed every time sun:home:phase:name is updated, how would this rule look like?
Can I use

when Channel "astro:sun:home:phase:name#event" triggered

or not? It is not listed as trigger channel. But from the rules-dsl documentation, I can only use triggered on channels.
Sometimes I see #name instead of name#event. How to know what syntax/scheme is correct?

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