Get id of row in table data

I was following this example : 

I have a question: How this “id” was generated?

Please help me. Tks!

Hello Tanhd!

ID is a value that is generated automatically by each table row. ID is like a primary key in which by specifying it, you can update row’s value; therefore, you cannot change the ID value.

As you may already know, you can verify its ID by looking at the event object.