Read this post: Introduction to Automation
First thing is to understand the difference between an event and a condition. That post is a starting point to get that understanding. Also, read this: [Released] Rule 4.0 (the top of this topic).
That post will help you understand the transformation of the original Rule Machine to the current Rule 4.0, and the reasons for the changes. The idea is to make things explicit that had been implicit. What we learned is that lots of users would stumble over anything that was implicit, and ended up mistakenly adding explicit things. For example, since the events that fired a rule were implicit in the conditions, users would create a Triggered Rule, and effectively break the whole thing. Ultimately, one has to come to understand this distinction between events and conditions. Both are necessary to create automations, and the two are very similar. But, there is an importance distinction that must be appreciated.
An event happens from a device in an instant, and the result of that event becomes the condition of the device. A switch turns on (the event), the light becomes on (its condition). If we want to automate something when the switch turns on, we need an event to trigger that automation. If we want to decide what to do based on whether or not the light is on, we need a condition to test the state of the light. These are two different concepts, both essential, yet still, different.
