By Yuval Halevi.

User Lifetime Value (LTV) is the measure of a user’s worth over a period of time. It helps determine the quality of your users. Even if a user doesn’t prove his value to the company directly by spending money on in-app purchases, they could still be of high-value if they share the app with their friends, spreading the word.

https://medium.com/swlh/user-lifetime-value-is-key-to-startup-success-4318ae82e432