Beyond the definition of traditional marketing relying on the traditional medium of marketing (TV, Print, Radio, Out-of-home etc.) and digital marketing on the digital medium (Internet, mobile etc.), here are the 3 key differences ...
Outreach: Digital marketing gives you access to a global market in an instance, as opposed to traditional marketing which has its strong-hold on local markets.
Customization: Digital lets your customize your message and offering to the target audience in real-time making it highly contextual, something that traditional medium has struggled to achieve.
Measurement: The ability to measure and maneuver a campaign in real-time is a marketer's wet dream which is possible using digital marketing. In traditional marketing, the metrics and measurement are based on approximations and sample sizes that may completely skew perception from reality.