What is an identifier?

I noticed references to an item (row) identifier, for example documentation of Outline at omni-automation.com. Outside of scripting what is an identifier, how do I set it, and how do I use it?

Each row in a document has a unique ID that is generated when the row is created. These IDs are used to know where in the outline hierarchy the row belongs. They can not be manually set nor viewed via the UI. It is however the same value used for row links, e.g. omnioutliner:///open?row= hBHEfAJ7Rh1

Below is an example of the XML that represents a row:

<item id="hBHEfAJ7Rh1" parent-id="m6Nf2Le-Mz7" rank="0004">

In an Omni Automation script a “Row” can mean either an ItemTreeNode ir an Item. Can I get the ID from either of these? (If so, I could construct a URL like you showed in a script.)