digital marketing can be measured by major e-marketing tools such as affiliate programs, banner, website, SEO, social media, e-mail marketing, and mobile marketing.
Ghazi, you are talking about the Levers of digital marketing. digital marketing could be mesured with KPI (key performance indicators) and it depends of what you want to measure: for exemple if you want to measure the performance of an online campaigns you can use these indicators: cost per mille, clic through rate, cost per lead, cost per acquisition, Return on investment, but if you are more interested by the engagement on your website you can use these indicators : opt in registration, time spent on the web site...