A protocol allows us to define interfaces that can be type checked.
It's an alternative to abstract classes that don't rely on duck typing instead of inheritance.
As long as a class implements the protocol's methods it will pass the type checking.
There are many predefined protocols in the standard library but they are currently defined as abstract classes under collections.abc.
Examples include Iterable, Hashable, Callable, Sequence.
Advantages
Decoupling. We don't need to import anything to implement a protocol, while with inheritance we need to import the parent class.
It also mean that there's no risk of partial code execution in parent classes wit something like super().mymethod()
Limitations
Protocols can't be checked at runtime, e.g. with isinstance() unless you use the @runtime_checkable decorator.