The correct answer is Virtual Local Area Networks (VLANs). VLANs allow a network to be logically segmented into separate broadcast domains within the same switch, which can improve network performance and security by limiting broadcast traffic to specific segments of the network. This is an essential function of Layer 2 switches and is commonly used in office environments to separate different types of devices or departments. Port Security is incorrect because it is primarily used to restrict the devices that can connect to a port based on MAC addresses. Quality of Service (QoS) is used to prioritize certain types of network traffic, which would not segment the network into different broadcast domains. Spanning Tree Protocol (STP) is used to prevent network loops in a network with redundant paths, not for segmenting traffic.