Digital marketing is a new version of an old term. It has been called things like inbound marketing. Basically, it is a term for the marketing methods that are used to target today’s audience.
Digital marketing is convenient slang that we use to describe any marketing efforts that just so happen to appear online or in other forms of digital Media. It is not a subset of actual marketing. It’s nothing more than marketing on digital media—websites, apps, blogs, social media, etc.