Explanation: A placement group is a logical grouping of instances within a single Availability Zone. Usingplacement groups enables applications to participate in a low-latency, 10 Gigabits per second (Gbps)network. Placement groups are recommended for applications that benefit from low networklatency, high network throughput, or both. Reference: http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/placement-groups.html