An A (Address) record is a type of DNS (Domain Name System) record that maps a domain name or subdomain to its corresponding IPv4 address. It is used to resolve domain names to specific IP addresses, allowing browsers and other clients to locate and communicate with web servers and other network resources.

When a user enters a domain name or subdomain in their browser, the DNS resolver queries the DNS system to obtain the corresponding IP address. The A record is the most common type of DNS record used for this purpose. It associates the domain name or subdomain with the IP address, enabling the client to establish a connection with the correct server.

Here’s an example to illustrate the usage of an A record:

Let’s say you have a domain name called example.com and you want it to point to the IP address 192.0.2.123. You would create an A record for example.com with the IP address set to 192.0.2.123. When someone enters “example.com” in their browser, the DNS resolver will look up the A record for example.com and retrieve the associated IP address. The browser then uses that IP address to connect to the web server hosting the website.

A records are also used for subdomains. For instance, if you have a subdomain called blog.example.com and you want it to point to a different IP address, you can create an A record specifically for the subdomain.

It’s important to note that A records are specific to IPv4 addresses. For mapping domain names to IPv6 addresses, AAAA (IPv6 Address) records are used. Additionally, changes to the IP address of the server require updating the corresponding A record to ensure the correct resolution of the domain or subdomain.