Glossary
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Plain-language definitions of the DNS, domain, SSL and infrastructure terms you'll actually run into.
DNS
12- A record
- An A record is a DNS resource record that maps a domain name to an IPv4 address (32-bit number), enabling browsers and applications to find your server on the internet.
- AAAA record
- An AAAA record is a DNS record that maps a domain name to a 128-bit IPv6 address, serving as the IPv6 counterpart to the A record.
- CAA record
- A CAA record is a DNS record type that authorizes which Certificate Authorities are permitted to issue TLS/SSL certificates for a domain.
- CNAME record
- A CNAME record is a DNS record that maps an alias hostname to its canonical (true) hostname, causing resolvers to look up the target name instead.
- DNS
- DNS (Domain Name System) is a hierarchical, distributed database that translates human-readable domain names like example.com into IP addresses and other resource records needed to locate services on the internet.
- DNS propagation
- DNS propagation is the time it takes for a DNS record change to become visible everywhere, caused by the delay until cached copies of the old record expire at each resolver.
- DNSSEC
- DNSSEC (DNS Security Extensions) is a suite of protocols that add digital signatures to DNS records, allowing resolvers to verify that DNS responses are authentic and unmodified.
- MX record
- An MX record is a DNS resource record that specifies the mail server responsible for accepting email on behalf of a domain.
- NS record
- An NS record is a DNS resource record that identifies which name servers are authoritative for a domain or subdomain.
- Reverse DNS
- Reverse DNS (rDNS) is the DNS lookup process that resolves an IP address back to a domain or hostname using PTR records, the inverse of a normal forward DNS lookup.
- TTL
- TTL (Time To Live) is a numeric field in every DNS record specifying the maximum number of seconds a resolver or cache can store that record before it must be re-fetched from the authoritative nameserver.
- TXT record
- A TXT record is a DNS resource record that stores arbitrary text data associated with a domain, commonly used for email authentication policies, domain verification, and other machine-readable configuration.
Domains
6- Apex domain
- An apex domain is the root domain name without any subdomain prefix, such as example.com rather than www.example.com, and must host the SOA and NS records for the DNS zone.
- Domain registrar
- A domain registrar is an ICANN-accredited business that sells domain names and manages registrations on behalf of customers by communicating with the authoritative registry for each top-level domain.
- Glue record
- A glue record is an A or AAAA record that a parent DNS zone publishes alongside a nameserver delegation to provide the IP address of a nameserver whose hostname is within the delegated child domain.
- Nameserver
- A nameserver is a server that stores DNS records for a domain and answers queries to resolve domain names into IP addresses and other zone data.
- Subdomain
- A subdomain is a domain name that is subordinate to a registered domain in the DNS hierarchy, created by prepending one or more labels to the parent domain (e.g., mail.example.com is a subdomain of example.com).
- WHOIS
- WHOIS is a protocol and database system that records and makes publicly queryable the registration details of domain names, including registrant information, registrar, creation/expiration dates, and nameservers.
- DKIM
- DKIM (DomainKeys Identified Mail) is an email authentication method that uses cryptographic signatures to verify that a message was sent from and authorized by a specific domain, and that its content was not altered in transit.
- DMARC
- DMARC (Domain-based Message Authentication, Reporting & Conformance) is an email authentication policy protocol that lets a domain owner publish a DNS record instructing receiving mail servers how to handle messages claiming to be from that domain that fail SPF and DKIM checks.
- SPF
- SPF (Sender Policy Framework) is an email authentication protocol that publishes a DNS TXT record listing IP addresses and servers authorized to send email on behalf of a domain, allowing receiving mail servers to verify the sender's identity.
SSL/TLS
6- Certificate authority
- A certificate authority (CA) is a trusted entity that issues and digitally signs SSL/TLS certificates after verifying the identity of the requester, establishing a cryptographic chain of trust.
- HTTPS
- HTTPS is HTTP layered over TLS encryption, ensuring confidential and authenticated communication between a browser and web server using an X.509 certificate.
- Let's Encrypt
- Let's Encrypt is a free, automated nonprofit Certificate Authority that issues domain-validated SSL/TLS certificates via the ACME protocol.
- SSL certificate
- An SSL certificate is a digital credential signed by a Certificate Authority that binds a public cryptographic key to a domain name, enabling servers to prove their identity and establish encrypted TLS connections with clients.
- SSL/TLS
- SSL/TLS is a cryptographic protocol that encrypts and authenticates data transmitted over networks, securing communication between clients and servers.
- Wildcard certificate
- A wildcard certificate is an SSL/TLS certificate with a hostname containing a leading asterisk (e.g., *.example.com) that secures an unlimited number of first-level subdomains with a single certificate.
Monitoring
2- SLA
- An SLA (Service Level Agreement) is a formal, measurable commitment between a service provider and customer defining expected performance levels such as uptime percentage, response time, and support response times.
- Uptime monitoring
- Uptime monitoring is automated, repeated checking of a server, website, or service at regular intervals to detect when it becomes unavailable and alert you to outages.
Network
3- Dynamic DNS
- Dynamic DNS (DDNS) is a method that automatically updates DNS records when an IP address changes, allowing a hostname to stay current without manual edits.
- IPv4
- IPv4 (Internet Protocol version 4) is the fourth version of the Internet Protocol, using 32-bit addresses to route packets across networks and the internet.
- IPv6
- IPv6 is the successor to IPv4, using 128-bit addresses instead of 32-bit addresses to provide vastly more available addresses for internet-connected devices.
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