Economics is as Arun shared from my understanding pretty much. It is the study of behavior(s) with consumption, organization, and allocation of resources whether tangible or intangible. Economics is a study of actions and acts with a capacity to predict within confines of criteria. It is a social science study based on business principals and or market (system) types, i.e. socialism, capitalism, and etc. Economics cannot cause an affect with an effect itself. The result of actions and acts is the economics. So, it is science.
Its observation can be expressed as an art form. A graph is an art form and is used with consistency to report factors of economics. Yet, the economy is not the art, it is what is observed. Just like a painter painting a scenic mountainside. The artist did not create the mountainside with the art of painting.
The mountainside (economy) can change. Yes, the artist could be the cause of the change with cutting down trees, planting trees, moving boulders somehow, and etc, yet that is not the artist as a painter doing that work. The same as an economist does not change the economy. It is, for instance, the investors in a capitalist market creating an economic change. The economist only observes the change of economy and reports it. Again, how it is reported could be an art form - writing, graphs, and economic model structuring.