How to run the following exports: Customer Base and Customer Addresses?

A company is switching one of my Magento 2 websites to Shopify (or some system like that) and they asked the following:

We were unable to run the following exports. Can you please provide them?

Customer Base
Customer Addresses

I have 2 questions:

1. What is that? Specifically, what is customer base – what is that referring to?
2. How can I provide those exports to them? Is it via Magento Admin or MySQL?

Exact steps would be very much appreciated.