Hi @Agolab,

Thanks for sharing this with us.

In Klaviyo, we’ll look to segments to help us organize users based on their activity in your account. That is because segments are designed to automatically reorganize (add and remove) users when that user takes some action (whether they unsubscribe, join another list, place an order, view a product etc.) the possibilities are endless. This is unlike lists which are designed to hold users for a specific purpose (i.e. subscribers to your brand, contest sign-ups etc). Often, lists are used as a “base” in the segment definition. For example, if you want to capture non-customers you could define a segment: “is in list > non-customer AND placed order zero times over all time”. This segment will filter out anybody who’s in this list and has placed an order. If they’re all true non-customers, the segment will include everybody. Moving forward, if a user is in this list and places an order, they will be automatically removed from the segment. In short, anyone in this segment will be a non-customer by definition, and you can send your “non-customer” email correspondences to this segment. For a more detailed breakdown of lists vs. segments, I recommend looking through our article here.

Now, flows have five separate types of triggers (List, Segment, Metric, Price Drop, Date triggers), you can use that same segment definition to build a flow (automation) for that non-customer segment. Say you wanted to send to customers, you could leverage the “Placed Order” metric to create a flow (automation) specifically for those who purchase (customers). Or you could use a segment (what somebody has done > placed order at least once over all time) as the trigger, however the advantage of using a metric is that it allows you to dynamically pull in event variables into your emails like the item price, image etc. which is helpful.

You may also find this article helpful on AND vs OR which is a common point of confusion when building segments. 

I hope that information is helpful :) 

Ok, so in my particular case i should not remove the contacts as they are moved automatically from one list to the other, if I define them correctly. 
Thank you for your clarification.