Powerhouse users can control who receives dynamic content based on listener tags.
That field is an "OR" field, meaning any listener with Tag 1 OR Tag 2 OR etc. will receive the preroll and postroll you decide.
You can combine this with "Starts At" and "Ends At" dates in an AND way. Meaning, the listener must have a tag AND it must be between the dates/times for them to receive the dynamic content.