Normal Identities
From Legacy Roblox Wiki
Every script in the DataModel must have an identity, or security context to outline which methods, properties and events are usable or not. Most of the time, prevention of using certain members of an object is strictly for security reasons. Other times, it may just be that the object being used is not fully developed yet.
Identity Levels
Below is a list of code types and their associated identity level:
Document Scripts (Local URL) and Plugin Scripts have an identity of 1.
Library Scripts, LocalScripts and Scripts have an identity of 2.
CoreScripts have an identity of 4.
Command Bar Scripts (Remote URL) and StarterScripts have an identity of 5.