A firewall is a system designed to prevent unauthorized access to or from a private network. You can implement a firewall in either hardware or software form, or a combination of both.
Uses
Prevents unauthorized actions from strangers on personal network.
Hardware & software to protect one’s gadgets from malicious attacks from viruses.
Features
Bandwidth controlling and monitoring becomes easy with firewall as with available bandwidth available users and applications can be monitored.
Web filtering enables to block unnecessary webpages, which you do not want users to access.
Logging
Deep packet inspection
Benefits
Monitors traffic
Keeps hackers and trojan viruses at bay.
Having firewall will keep keyloggers from monitoring you.