Mediator pattern defines a separate (mediator) object that encapsulates the interaction between a set of objects and the objects delegate their interaction to a mediator object instead of interacting with each other directly.
翻译成中文就是：中介模式定义了一个单独的（中介）对象，来封装一组对象之间的交互。将这组对象之间的交互委派给与中介对象交互，来避免对象之间的直接交互。