Shopify Winback Flow Automation

I am trying to setup Shopify's winback flow and am a little confused (or just need a clarity). I have created a customer segment based on my requirements, and I have also setup the flow. The question I have is does this automation run every time a customer is added to segmentation? When the automation flow runs, do all the customers in the segment receive the e-mail or only the ones that were added to the segment list? Also, is this segment list automatically updated everyday?