Unlike most offline marketing efforts, digital marketing allows marketers to see accurate results in real time. If you've ever put an advert in a newspaper, you'll know how difficult it is to estimate how many people actually flipped to that page and paid attention to your ad. There's no surefire way to know if that ad was responsible for any sales at all.
Marketing requires creativity. That creativity can come in many forms. Graphic designers put together visual presentations to attract customers. Writers create content that is designed to engage the reader and keep them interested. A programmer writes code to create a web page that is easy to navigate. Regardless of your marketing role, you need to think creatively.