Packet Filtering is a network security technique that controls the flow of data packets between devices. It examines each packet's header information, such as source and destination IP addresses and port numbers, to determine whether to allow or block the packet based on predefined rules. This helps protect networks from unauthorized access and various types of attacks. By implementing firewalls that use packet filtering, organizations can create a barrier between their internal networks and external threats. This method is efficient and can quickly process large volumes of traffic, making it a fundamental component of network security strategies.