The firewall protects your computer from intrusions or attacks across the Internet, and at the same time lets you share files and printers with other computers on the local network.
When your PC connects to a network, the firewall applies a security level in accordance with the type of network. If it is a trusted network (e.g. local), the firewall protection will apply security settings that let you share folders and printers with other computers on the network.
If your PC connects to a public network (cyber cafés, airports, etc.), the firewall applies a more restrictive security level to prevent other users on the network from accessing your shared resources.
If you want to share files or printers with other users on a trusted network, make sure the network adapter you use is associated to the trusted network.
For more information, refer to the section on Configuring the firewall security level.