| A record |
DNS record mapping a name to an IPv4 address |
| AMI |
Amazon Machine Image — template (OS + software) to launch EC2 instances |
| Auto Scaling group (ASG) |
Group of EC2 instances that AWS adds/removes automatically based on demand or health |
| AZ (Availability Zone) |
One or more isolated data centres within an AWS Region |
| Block device mapping |
Part of an AMI/launch that lists which volumes (root, data) attach to an instance, their device names, sizes and types |
| Bastion host |
A hardened server used as the only SSH entry point into private subnets |
| CNAME |
DNS alias record pointing one name to another name; not allowed at the apex |
| CIDR |
Classless Inter-Domain Routing notation, e.g. 10.0.0.0/16 |
| cloud-init |
Tool that configures an instance at first boot (runs user data, grows root partition) |
| Daemon |
Background service process (e.g. sshd, nginx) |
| DLM (Data Lifecycle Manager) |
AWS service that automates creation and deletion of EBS snapshots and EBS-backed AMIs |
| DHCP |
Protocol that assigns IP addresses automatically |
| DNS |
Domain Name System — translates names to IP addresses using a hierarchy of root, TLD and authoritative name servers |
| Document root / DocumentRoot |
Folder from which a web server serves files (root in Nginx, DocumentRoot in Apache) |
| EBS |
Elastic Block Store — persistent block storage volumes for EC2 |
| EC2 |
Elastic Compute Cloud — AWS virtual servers |
| Elastic IP |
Static public IPv4 address allocated to your AWS account |
| ELB (Elastic Load Balancer) |
Managed load balancer (ALB/NLB) that spreads traffic across instances |
| ENI |
Elastic Network Interface — virtual network card of an instance |
| FastCGI / PHP-FPM |
Protocol / process manager that lets web servers run PHP efficiently |
| firewalld |
Dynamic host firewall used on RHEL/CentOS |
| FQDN |
Fully qualified domain name, e.g. blog.example.com. |
| fstab |
/etc/fstab — file listing filesystems to mount at boot |
| Golden AMI |
Standard, patched, pre-configured image from which all servers are launched |
| Gunicorn |
Production WSGI HTTP server for Python web apps |
| Horizontal scaling |
Adding/removing instances (scale out/in), usually with ASG + ELB |
| IAM |
Identity and Access Management — users, groups, roles and policies in AWS |
| IGW |
Internet Gateway — connects a VPC to the internet |
| IMDS |
Instance Metadata Service at 169.254.169.254 (use IMDSv2 tokens) |
| IOPS |
Input/output operations per second — storage performance measure |
| Key pair |
Public/private key used for SSH authentication to EC2 |
| LTS |
Long Term Support release (e.g. Ubuntu 24.04 LTS, Node.js LTS) |
| NAT |
Network Address Translation — maps private IPs to a public IP |
| NAT Gateway |
AWS managed service giving private subnets outbound internet access |
| Name server (NS) |
Authoritative DNS server that answers queries for a domain; set at the registrar |
| NACL |
Network Access Control List — stateless subnet-level firewall |
| Nitro |
AWS hypervisor/hardware platform; EBS appears as NVMe devices |
| pm2 |
Production process manager for Node.js applications |
| Port |
16-bit number identifying a service on a host (0–65535) |
| Registrar |
Company that registers and renews domain names (GoDaddy, Namecheap, Route 53 Domains) |
| Region |
Geographic area containing multiple AZs, e.g. ap-south-1 (Mumbai) |
| Reverse proxy |
Server (Nginx/Apache) that forwards client requests to backend apps |
| Route 53 |
AWS DNS service: hosted zones, records, Alias records, domain registration |
| RFC 1918 |
Standard defining private IPv4 ranges 10/8, 172.16/12, 192.168/16 |
| Scale up (vertical scaling) |
Moving to a bigger instance type (more vCPU/RAM); needs stop/start |
| Server block |
Nginx server { } section defining one website (port, server_name, root) |
| Security group |
Stateful virtual firewall attached to instances/ENIs |
| SELinux |
Security-Enhanced Linux — mandatory access control on RHEL/CentOS |
| Service quota |
Per-account, per-region limit on resources (e.g. 5 Elastic IPs by default) |
| Snapshot |
Incremental point-in-time backup of an EBS volume |
| SPA |
Single Page Application (React, Angular) |
| Subdomain |
Name to the left of your domain, e.g. blog.example.com; created free with a DNS record |
| Subnet |
A range of IP addresses within a VPC, located in one AZ |
| systemd |
Linux init system and service manager (systemctl, journalctl) |
| TLD |
Top-level domain such as .com, .in, .org |
| TLS/SSL |
Encryption protocol used by HTTPS |
| TTL |
Time To Live — seconds a DNS answer may be cached by resolvers |
| User data |
Script passed to an instance that runs at first boot |
| UUID |
Universally unique identifier of a filesystem, used in fstab |
| Virtual host |
Apache <VirtualHost> section defining one website; name-based vhosts share one IP and port |
| VPC |
Virtual Private Cloud — your isolated network in AWS |
| WSGI |
Python standard interface between web servers and Python apps |