Hi @brinbag, welcome to the community!

It’s a great question - and a common one at that so don’t feel like you’re alone.  Not to mention, Klaviyo uses “Flow Filters” and “Trigger Filters” sometimes interchangeably, so it can be a bit confusing.

You can see some official documentation here:

• Understanding flow triggers and filters

But the way to think of it is this way:

• Flow (aka Trigger) Filters - are filters based on the Triggered event’s data. That also means, Trigger Filters are only available for Metric based Flows - Flows that occur when a metric/event happens (such as Checkout Started, Placed Order, etc).  It lets you filter based on the various data specific to that Trigger only. 
• Profile Filters - are filters based on any profile properties or actions of the user, it doesn’t even have to be related to the Trigger event.  This could be various properties or custom properties, or any other events.

Use Flow Filters to restrict certain people entering the Flow based on aspects of that Trigger.  Use Profile Filters for other events or profile data unrelated to the Trigger.  Both will restrict people from entering (or staying) in the Flow - and you can use a combination of them as you see fit.  

Hope that helps!