What is Amazon EC2?

Question

What is Amazon EC2?

Accepted Answer

**EC2** (Elastic Compute Cloud) provides resizable **virtual servers** (instances) in the cloud — you launch, configure, and run virtual machines on demand. It's one of AWS's core, foundational services for running applications.

## What EC2 is

```text
EC2 = virtual servers ("instances") you rent and run in AWS's cloud:
  → launch a VM in minutes (choose OS, CPU, memory, storage)
  → full control (it's your server — install software, configure as you like)
  → pay for the time it runs (per-second/hour)
  → "Elastic" — launch many, scale up/down, resize as needed
```

## Key concepts

```text
INSTANCE TYPE → the hardware profile: CPU/memory/network (e.g. t3.micro small,
  m5.large general, c5 compute-optimized, r5 memory-optimized) — pick by workload
AMI (Amazon Machine Image) → the template (OS + pre-installed software) to launch from
KEY PAIR → SSH keys to securely access (log into) the instance
SECURITY GROUP → a virtual firewall (which ports/traffic are allowed)
EBS VOLUME → attached disk storage (persists data)
ELASTIC IP → a static public IP address
```

## Launching and using an instance

```bash
# typically via the Console, CLI, or IaC:
aws ec2 run-instances --image-id ami-xxx --instance-type t3.micro --key-name mykey
# then SSH in:
ssh -i mykey.pem ec2-user@<public-ip>
# install/run your app on the instance like any Linux/Windows server
```

## Pricing models

```text
ON-DEMAND → pay per use, no commitment (flexible, most expensive)
RESERVED / SAVINGS PLANS → commit 1-3 years for big discounts (steady workloads)
SPOT → spare capacity at huge discounts, but can be reclaimed (fault-tolerant workloads)
```

## Why it matters

Understanding EC2 is fundamental because it's one of AWS's core, most-used services — providing the virtual servers that run a vast range of applications — so it's essential foundational AWS knowledge.

EC2 represents the basic cloud capability of **running virtual servers on demand**: launching virtual machines in minutes (choosing the OS, CPU, memory, and storage), having full control to install and configure software as needed, paying only for running time, and scaling elastically.

This is the cloud equivalent of having servers, making EC2 a foundational building block for hosting applications, websites, databases, and almost any workload.

Understanding the **key concepts** — instance types (matching hardware profiles to workloads), AMIs (templates to launch from), key pairs (secure access), security groups (firewall rules), EBS volumes (storage), and elastic IPs — is necessary to actually launch and use EC2 effectively.

Understanding the **pricing models** (on-demand for flexibility, reserved/savings plans for steady workloads at a discount, and spot instances for big savings on fault-tolerant workloads) is practically important for cost-effective use, a significant real-world consideration.

Since EC2 is a core, ubiquitous AWS service (the virtual-server foundation that runs countless applications) and understanding it (the concept, key concepts, and pricing models) is fundamental to working with AWS compute, understanding EC2 is essential, foundational AWS knowledge — one of the first services to understand when learning AWS and a building block underlying much of what runs on the platform, making it important knowledge for anyone working with AWS infrastructure.