Hiri has two modes to help you deal with your Inbox folder: Unified Inbox and Zero Inbox mode. These modes affect what happens when you move an email from your Inbox to Action/FYI filters on the left hand side. It reflects the two different approaches of how people manage their email.
Unified Inbox mode
In this mode your Inbox will contain all mails - Actionable, FYI and those that are unsorted. When you drag an email to Action/FYI filters, it will stay in your Inbox but will change colour to red (Action) or blue (FYI). Depending on where you dragged it, the email will appear in Action or FYI filters too.
Zero Inbox mode
This mode follows the Zero Inbox email management practice which aims to keep your Inbox empty or almost empty at all times. When you drag an email to Action/FYI filters, the email is moved to Action/FYI. You will no longer see emails that you dragged elsewhere when you click the Zero Inbox button.
This separation happens only in Hiri - if you browse your mail in another client (e.g. on your phone), all mails will still be in your Inbox.
You can switch between the two modes at any time, by going to Settings -> Preferences.