What does unwrapping a model do and why use this?

Hello, I’m trying to understand the code using accelerate.
There is a function name is “unwrap_model” and its contains below code.

accelerator.unwrap_model(model)

I read document about the function, " Unwraps the model from the additional layer possible added by prepare()". But I can’t even know that meaning “unwrapping” in “unwraps the model”.

I reallly want to know that What does unwrapping a model do and why use it.

thank you.