What is the name for a DNS record starting with @?

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http://serverfault.com – I know that DNS records starting with * are called Wildcard records. What is the name for DNS record starting with @ (the at symbol). This is a record for the root domain (e.g. just example.com, not www.example.com) I want to find out more, but searching for "@ record dns" in Google doesn't return any useful results. What is the official terminology for this type of record, and where might I find it described in more detail? (HowTos)