To put it shortly, it’s all about approaching marketing through the scientific method and using it to solve challenges in marketing. First you develop a hypothesis based on your observations and maybe intuition, let’s say it’s “TV is the best marketing channel to advertise Chocolate bars”.
Then you gather data, sales and marketing data in this case, analyse the data, develop a model of the reality, and test your hypothesis. In the end you will learn something. You can then develop a new hypothesis and continue the cycle. The key idea is to experiment, learn new things, and build on your learnings.