Explanation:
An Elastic IP address (EIP) is a static IP address designed for dynamic cloud computing. With an EIP, you can mask the failure of an instance by rapidly remapping the address to another instance. By default, all AWS accounts are limited to 5 EIPs, because public (IPv4) Internet addresses are a scarce public resource.
Reference: http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/elastic-ip-addresses-eip.html