The whole business world talks about (and chases) network effects. But there is a surprising amount of misunderstanding, also and especially among early-stage investors. When I talk about our vision for experify.io I always stress the point that our business model and (future) defensibility heavily relies on network effects. More often than not what I hear from the other side of the table is something in the line of:
You don't have network effects. Network effects is something you see in social networks leading to exponential user growth."
But that is not the network effect I am talking about. That is called virality. Clearly you can use networks to create virality / exponential growth, e.g. when every user invites > 1 users to your product, but it's not what is generally meant when talking about network effects.
Here is a link to an article by nfx, that very comprehensively explains the several types of network effects. The key take-away is: when talking about network effects, keep the following definition in mind:
A company is said to show network effects if its product(s) become not less, but more valuable with usage.
(By the way: Scott Galloway calls it the Benjamin Button effect -- which I like better, as it stresses the "more valuable with time" nature more and avoids the very common above misunderstandings.)