A working reference for the vocabulary of digital marketing and growth — organized by channel and discipline. Definitions are written for practitioners, founders, and analysts who move fast and need the concepts straight. Acquisition and Channels CAC (Customer Acquisition Cost) The total cost of acquiring a new customer — all sales and marketing spend divided by the number of new customers acquired in the same period. CAC is the fundamental unit economics metric on the cost side.

Watch how people buy things now and you’ll notice it’s no longer a neat funnel—it’s more like a looping, fragmented path where discovery, validation, and decision-making keep blending into each other. A product might first appear in someone’s life as a passing image in a feed, then resurface days later through a search, and finally get validated through a completely different channel. The journey isn’t linear anymore, and brands that still think in straight lines tend to miss where decisions are really happening.

Referral marketing always looked simple from the outside. You recommend something, someone signs up or buys, and you get rewarded. Clean, almost obvious. But underneath that simplicity sits a layered economic system that behaves less like traditional advertising and more like a distributed trust market—one where credibility, timing, and positioning quietly determine who captures value. What makes referrals different from most other marketing channels is that they compress the distance between awareness and decision.

Traffic looks impressive on dashboards. Big numbers, upward curves, spikes after a campaign—it gives the feeling that something is working. But spend enough time looking closer, and you start to notice the gap. Visitors arrive, scroll, maybe click around a bit… and then leave. No action, no commitment, no real outcome. It’s movement without momentum. Trust operates differently. It doesn’t always show up as volume, but when it does, it compresses the distance between interest and decision in a way traffic alone never can.