curl -- head is similar to curl get. Remember from your studies that get is when a user/entity is requesting to get/download resources from a server across the internet. Get requests include a header and a body. By doing curl --head, you're sending a request to get information from a server. The server will reply by providing only the headers of the request, rather than including the body. Therefore a curl -- head is a way to send requests for header-only get requests. This allows people a quick summary of a response server, or in this case, to view it's fingerprint.