What it means
A firewall app exception lets a particular application receive allowed traffic when it runs. An open port rule permits traffic through a named port until the rule is removed or disabled. Both change exposure, but Microsoft's consumer guidance treats an app exception as generally less risky than leaving a port open.
A real-world example
A game asks you to disable the firewall to fix multiplayer. First identify whether the game needs an inbound exception at all. If it does, select the official executable and the Private network rather than opening an arbitrary port on every network.
What to do
Keep the firewall on, add the minimum exception and test the feature. Remove old entries when uninstalling software; review Public network access particularly carefully.
The distinction that matters
The rule controls traffic, not software trust. A malicious program that is allowed through still remains malicious. Microsoft's firewall guidance gives separate steps to add and remove applications and port rules.
Microsoft's firewall risk guide
