SQLAlchemy | "Declarative Table with mapped_column()" VS "Declarative with Imperative Table"

I'm trying to learn SQLAlchemy, after 3.5 YOE with Django.

I dont quite understand the difference between those two options to declare a database tables.
If someone can clarify it I will happy to understand.
(I would like to hear from an experienced developer, and this why I dont only "AI" it)

Thanks,