Network effect is a concept based on the value that users get with every new user joining a service providing network or a marketplace.
The benefit that users get from the goods and services traded depends on the number of users that joined the network, as well as the compatibility of products, their value and utility.
Network effect can be one-sided like in the case of WhatsApp, Viber or Skype to name a few, and two-sided such as in Airbnb or eBay for example where both existing and new users benefit from one another.
