Glossary
Server and hosting terms, A to Z
Short definitions in plain language. Each one links to a full guide when there is more to know.
A
- A record
- A DNS record that points a hostname to an IPv4 address.
- AAAA record
- A DNS record that points a hostname to an IPv6 address.
- Apache
- A long-established open-source web server, known for per-folder configuration with .htaccess files.
B
- Bandwidth
- The amount of data a hosting plan lets your site send to visitors, usually measured per month.
C
- Cache
- A stored copy of something expensive to produce, kept so later requests can be answered instantly.
- CDN
- A content delivery network: servers around the world that keep copies of your files close to visitors.
- Certificate authority
- An organisation trusted by browsers to issue SSL/TLS certificates after checking who controls a domain.
- CNAME record
- A DNS record that makes one hostname an alias of another.
- Control panel
- A web interface for managing hosting without the command line, such as cPanel or Plesk.
- cPanel
- The most widely used hosting control panel, especially on shared hosting.
- Cron job
- A command scheduled to run automatically at set times on a Linux server.
D
- DDoS
- A distributed denial-of-service attack: flooding a site with traffic from many machines to knock it offline.
- Dedicated server
- A whole physical server rented to one customer.
- DKIM
- An email signature, checked against a public key in DNS, that proves a message came from your domain unchanged.
- DMARC
- A DNS policy that tells receiving mail servers what to do when SPF and DKIM checks fail, and where to send reports.
- DNS
- The Domain Name System, which turns names like example.com into the IP addresses computers use.
- Domain registrar
- The company you register and renew a domain name through.
F
- Firewall
- Software or hardware that decides which network connections may reach a server.
H
- HTTP status code
- The three-digit number a server sends with every response, saying whether the request worked.
- HTTPS
- Web traffic sent inside an encrypted TLS connection, shown by the padlock in the address bar.
I
- Inode
- A record the file system keeps for every file and folder; shared hosts often limit how many you may have.
- IP address
- The number that identifies a device on a network, such as 203.0.113.10.
L
- Latency
- The delay before data starts arriving, usually measured in milliseconds.
- Let's Encrypt
- A free, automated certificate authority that issues trusted 90-day HTTPS certificates.
- Load balancer
- A server that spreads incoming traffic across several backend servers.
M
- MX record
- A DNS record naming the mail server that receives email for a domain, with a priority number.
N
- Nameserver
- A server that holds a domain's DNS records and answers lookups for them.
- Nginx
- A fast, widely used web server and reverse proxy.
P
- PHP-FPM
- The service that runs PHP code for web servers like Nginx, using a pool of worker processes.
- Port
- A number from 0 to 65535 that directs network traffic to a particular program on a server.
- Propagation
- The time it takes for a DNS change to be seen everywhere, as cached copies of the old record expire.
R
- RAID
- A way of combining several disks so they act as one, for speed, protection against a failed disk, or both.
- Reverse proxy
- A server that receives requests on behalf of other servers and passes them along.
- Root access
- Full administrator control of a server, with permission to change anything.
S
- SFTP
- A secure way to transfer files to and from a server over an SSH connection.
- Shared hosting
- Hosting where many websites share one server and the host manages it.
- SPF
- A DNS record listing which servers may send email for your domain.
- SSH
- Secure Shell: an encrypted way to log in to and run commands on a remote server.
- SSL/TLS certificate
- A file that binds a domain name to a public key, signed by a certificate authority, enabling HTTPS.
- Subdomain
- A name inside your domain, such as blog.example.com or www.example.com.
T
- TTL
- Time to live: how many seconds resolvers may cache a DNS record before asking again.
- TXT record
- A DNS record that holds text, used for domain verification and email security.
U
- Uptime
- The share of time a site or server is available, usually given as a percentage.
V
- VPS
- A virtual private server: a virtual machine with guaranteed resources and full control, on shared hardware.
W
- Web server
- The software that receives requests from browsers and sends back pages and files.
- WHM
- WebHost Manager: the administrator side of cPanel, used to create and manage hosting accounts.
- WHOIS
- A lookup that shows a domain's registrar, registration dates, status and nameservers.