Digital marketing is the use of digital channels — search engines, social media, email, websites, and paid advertising — to connect businesses with customers. 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 (direct reach to people who opted in), and social media (brand awareness and community). Start with one or two channels and learn them well before adding more.