Digital marketing connects businesses with customers through search engines, social media, email, websites, and paid advertising. Unlike traditional marketing it’s measurable, targetable, and adjustable in real time. Core channels: SEO (free organic traffic, highest long-term ROI), paid advertising (immediate results), content marketing (builds trust and compounding traffic), email marketing ($36 ROI per $1 spent), and social media. Start with one or two channels, learn them well, then expand.