Jitter refers to the variation in packet delay at the destination, which can lead to packets arriving out of order. This can significantly affect real-time applications like VoIP, as it relies on the consistent timing of packet arrival. Monitoring and reducing jitter is crucial for improving voice call quality. Bandwidth, while related to network capacity and can impact overall network performance, does not directly address variations in packet delay. Latency measures the time a packet takes to reach its destination but does not account for the variation in delay between packets. CPU usage is an important device performance metric but is not directly related to the timing and order of packet delivery for VoIP quality issues.