Action

Action automation line will preform a function on Layers, Items, Keyframes and more.

The action manipulate the object in multiple ways that may or may not affect the properties of the object, we can take a look at 2 properties of the layer object "move to beginning" and "duplicate", duplicate will not affect any property of this layer and "move to beginning" will affect the "index" property of this layer (the new index value will be 1).

Some actions require a specific input like layer, project, item, number, text in order to successfully work, the action will show only the properties that can be accepted by the specific action.

The difference between property and action -

Properties and action can look very similar at times because sometimes a change in property value can preform a function, for example setting the "start point" of a layer will move the layer in the timeline, on the other hand the action "move to beginning" will also move the layer position in the timeline so what is the difference?

The main differences are that action will only preform a function while a property stores a value and may preform a function too, a property value can be used in other automation lines while action is only accessible through the action automation line.

Calculations -

The action automation line can't preform calculations like a set automation line, this feature isn't planned to be implemented so if you need to make a calculation you should use the set automation line and then use the result in the action automation line.