Unknown Callers are directly sent to voicemail, having no chance of disturbing you. Decide on your own when you want to review past calls and the callers' voicemail messages.
Known Callers will not let your phone ring but only send a notification to your phone. Review the call reason through Unlined's transcripts and decide if you want to answer.
Create a list of Trusted Callers. They are the only ones who can get directly through to you. And if you're busy, Unlined informs your Trusted Caller so they know to only ring for urgent cases.