the.com/network effect

means The economic phenomenon where a product or service becomes more valuable to every user as more people use it, because the value comes from the connections between users rather than the product alone.

from Coined in economics and telecommunications discussions of the mid-20th century, originally to explain why a telephone was useless with one subscriber but indispensable with millions — each new phone added value not just for itself but for everyone already connected. The term stayed mostly academic until the rise of computer networks and later the internet, when it became the favorite explanation for why platforms like social networks, marketplaces, and operating systems tend toward winner-take-most dynamics: being first and biggest becomes its own gravitational pull.