Identifiers are names given to objects so you can manipulate them easily.

create sprite 16 as "player"
zoom "player" to 2
create text "hello world" as "hello"
delete "hello"

You can use a name, a number, or a variable:

create text "hello world" as 1?obj = "temp"
create text "hello world" as ?obj

Except for sprites, objects can use their default name if none is provided:

create light
color "light" to #FF0
create text "Hey"
zoom "Hey" to 2