When is the colon at the beginning written in the update attribute?

Question

Java

When is the colon at the beginning written in the update attribute?
those. there are several forms of update, I want to finally understand when what is used
:FORM:id
:id
FORM:id
id
What is the difference between :FORM:id and FORM:id

Answer 1

The difference is that: in front of the path indicates the root form, the absence of it indicates that update has access to this id (in this case, FORM), without specifying the full path to it