Understanding Decorators in Python
Decorators are wrappers around Python functions (or classes) that change how these classes work. A decorator abstracts its own functioning as far away as possible. The Decorator notation is designed to be as minimally invasive as possible. A developer can develop his code within his domain as he is used to and only use the decorator to extend the functionality. Because this sounds very abstract, let’s look at some examples.
Source: Understanding Decorators in Python, an article by Bas Steins.