Cosmology is the branch of astronomy that studies the origin, evolution, and structure of the universe as a whole. It encompasses both the theoretical and observational aspects of understanding the cosmos.

Here's a breakdown:

* Knowledge about the universe: Cosmology seeks to understand the fundamental properties of the universe, such as its size, age, composition, and evolution.

* Method of obtaining that knowledge: Cosmologists use a variety of methods to gather data, including:

* Observational astronomy: Using telescopes to observe distant objects and phenomena.

* Theoretical models: Developing mathematical models to explain observations and make predictions.

* Computer simulations: Simulating the evolution of the universe on a computer.

So, cosmology encompasses both the knowledge about the universe and the scientific methods used to acquire that knowledge.