AWS Certified Solutions Architect Associate Test 7

A placement group is a logical grouping of EC2 instances within a single Availability Zone. Usingplacement groups enables applications to participate in a low-latency, 10 Gbps network.
Placement groups are recommended for applications that benefit from low network latency, highnetwork throughput or both.
Reference: http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/placement-groups.html