A DNS hostname is a human-readable name assigned to a resource, such as an Amazon EC2 instance, that maps to its IP address. It allows users to access the resource using a name instead of a numeric IP address.
In AWS, when DNS hostnames are enabled for a VPC, EC2 instances with public IP addresses receive a public DNS name that can be used to connect to the instance.
In simple words, a DNS hostname is the name of a server or resource that DNS translates into an IP address, making it easier to access.