What does the @ symbol represent when used inside of a DNS zone?

Question

What does the @ symbol represent when used inside of a DNS zone?

Answer

When editing a DNS zone, you can use the @ symbol to reference the base domain of the zone.

For example, if you are editing the zone for example.tld, you could write an A record like this:

@    IN    A    192.0.2.2  ; IPv4 address for example.com

That would be equivalent to:

example.com    IN    A    192.0.2.2 ; IPv4 address for example.com

This is outlined in the following RFC on page 34

RFC 1035 - Domain Implementation and Specification