Lumen

The Lumen allows you to truly take ownership of all of your data. It acts as your personal data centre where all of your data and content is stored.

Basically, Lumen authenticates you in the lens network. What is lens?. The lens is a network of people it's not a platform lens just make sure to connect you with people directly. so there are two ways to connect with lens

1. Lumen
2. Pc
   The purpose of these devices is to store your data and facilitates your interactions on Lens.

So if you don't have a laptop then you need to purchase Lumen. It allows you to do 2 things

First once you're connected in the peer-to-peer network you are able to use the internet without having to sign up for a service such as Google or Facebook.

so basically you are cutting out the middle man and connecting straight with people

Secondly it allows other peers, such as your pc or phone to handle all the computations.src.