When you type example.com, how does your browser know where the site is? Thanks to DNS, the directory of the Internet. It is an invisible but essential cog — and knowing how to read it prevents many mistakes.

The principle: a giant directory

Computers do not talk to each other using names, but using IP addresses (numbers). DNS (Domain Name System) does the translation: it turns example.com (human-readable) into 168.231.83.229 (the server’s address).

It works exactly like a phone book: you look up a name, it gives you the number.

The journey of a DNS request

1. You type example.com.
2. Your computer asks a resolver (often the one provided by your ISP): “what is the address of example.com?”
3. The resolver queries the domain’s name servers and gets the address.
4. Your browser can then contact the server.

To speed things up, each step keeps the answer in cache for a certain time.

The main records

A DNS zone contains several types of records. The most common ones:

Type	Role
A	Points the domain to an IPv4 address
AAAA	Same, in IPv6
CNAME	Points a name to another name (alias, e.g. www)
MX	Indicates the domain’s email servers
TXT	Free text: verifications, anti-spam (SPF, DKIM)

⚠️ Touching the MX or TXT records can break your email. When you repoint a site (A record), you do not touch the MX/TXT.

Propagation: why it takes time

When you change a record, the update is not instant everywhere. Resolvers keep the old answer in cache for a duration called TTL (Time To Live). You therefore have to wait for that cache to expire: from a few minutes to a few hours.

That is why, after a DNS change, some people already see the new site while others still see the old one: this is normal, the time it takes to propagate.

Key takeaways

• DNS translates names into addresses.
• The A record points the site; MX handles the emails — do not confuse them.
• A change propagates gradually (be patient).

DNS is managed at your registrar or your host. A mistake here can make a site (or its emails) unreachable — hence the importance of understanding what you are changing.