Observer Design Pattern vs “Listeners”

Question

It seems to me that the Observer design pattern as described in GOF is really the same thing as Listeners found in various toolkits. Is there a difference between the concep

Answer 1

There's a two-way nature to the description of Observer in Design Patterns by Gamma et. al. (GoF).

In their description of Observer, one of the ConcreteObservers might signal a change to its Subject. The Subject, which holds a list of all ConcreteObservers, then notifies its list. All ConcreteObservers, including the prime mover, then react as appropriate.

The common implementations of Listeners seem to all react to events from outside.

So, I would say that the Listener is a less-generalized case of an Observer.