Type a website name into a browser and you never see the number the network actually uses to find it. Something quietly translates that name into an address, and if that translation is wrong, everything downstream breaks. That translation lives in DNS records, and knowing the common types is how you tell a "name" problem from a "network" problem.
This is CompTIA A+ Core 1 (220-1201), Networking Objective 15, which groups DNS with DHCP, VLANs, and VPNs. For the DNS portion, the exam expects you to recognize the standard record types by name and know what each one does. This article stays on the records themselves: A, AAAA, CNAME, MX, and TXT, plus how a technician actually reads them with lookup tools.
DNS records are the entries that map names to answers
The Domain Name System is a distributed database that answers questions about domain names. Each answer comes from a record, and each record has a type that tells the resolver what kind of information it holds. When you ask for a website, you're really asking a DNS server to return the record that matches your question.
Every record shares a few common parts. There's the name it applies to (like example.com), the type (like A or MX), the value it returns (an address, a hostname, or text), and a TTL, or time to live. TTL is the number of seconds a resolver is allowed to cache the answer before asking again. A low TTL means changes propagate quickly; a high TTL means less traffic but slower updates. On the job, TTL is why a DNS change you made "isn't working yet" for some users but works for others.
In exam terms, you don't need to configure a zone file from memory. You need to match the record type to its job. The five types below cover almost everything A+ will ask.
A records point a name to an IPv4 address
An A record (Address record) maps a hostname to an IPv4 address. This is the workhorse of DNS. When www.example.com resolves to 93.184.216.34, an A record is doing the work.
A single name can have more than one A record, each pointing to a different IP. Resolvers rotate through them, which spreads traffic across servers in a simple form of load distribution. That's why a large site can return a different address each time you look it up.
For a technician, the A record is the first thing you verify when a user can reach a site by IP but not by name. If the ping to the IP succeeds but the name fails, the A record (or the path to the DNS server) is where you look. It's also what you edit when you host an internal service and want a friendly name like printserver to reach 192.168.1.50.
AAAA records do the same job for IPv6
An AAAA record (spoken as "quad-A") maps a hostname to an IPv6 address. It exists because an IPv4 address is 32 bits and an IPv6 address is 128 bits, so the older A record simply can't hold it. The four A's are a reminder that IPv6 is four times the size of IPv4.
A modern domain often has both an A record and an AAAA record for the same name. A device with IPv6 connectivity may prefer the AAAA answer, while an IPv4-only device uses the A record. This dual setup is normal and is not a misconfiguration.
The gotcha worth remembering is that AAAA problems can hide. A site may load fine for one user and fail for another because one machine tried the IPv6 address and couldn't route to it, while the other used IPv4. When you see intermittent name-resolution failures on newer networks, check whether an AAAA record is returning an address the client can't actually reach.
CNAME records make one name an alias for another
A CNAME record (Canonical Name record) points one hostname to another hostname rather than to an IP address. It creates an alias.