A common Terraform mistake is trying to access a resource created inside a module directly from the root configuration.
It fails, and the error feels confusing at first.
The reason is simple once you see it clearly.
Modules create a boundary.
That boundary hides internal resource addresses.
Terraform does not allow the root module to reach inside and grab values directly.
It forces you to define exactly what should be exposed.
That is where module outputs come in.
An output is not just a convenience.
It is a contract.
It takes a value from inside the module and makes it visible outside, without exposing everything else.
Once you understand this, module behavior becomes predictable.
You stop guessing resource names.
You stop breaking configurations during refactors.
You start designing modules the same way you design systems.
Clear boundaries.
Explicit interfaces.
Controlled exposure.
That is the shift.