Think about the last time you bought sneakers, picked a restaurant, or chose a phone. Did you ask a friend? Read online reviews? Maybe you just noticed what everyone else was wearing. The truth is, most purchases are shaped by other people — whether we know them personally or only admire them from afar. They affect what we want, what we trust, and what we finally buy. In this chapter, we’ll explore how those social forces work and why understanding them is a powerful tool for any marketer.