Allow or Block

Hello everyone

Who can explain the picture below. What happens to select Allow or Block? What is the risk that?

See if this helps CIS ver5: System(4) Listening port on: 445 question

I also get these types of popups with CIS default Network Security Policy. I use Stealth Port Wizard last option i.e Block all Incoming Connection & no such popups with this setting. I prefer this setting as its the safest for average users & I dont do P2P, etc. So this setting is apt for me.