1. What Is a Service in Compose?

In Docker Compose:

services:
  server:
    ...

A service is:

• A definition of how to run a container
• With its configuration
• Network attached automatically
• Can be scaled
• Can depend on other services

Important distinction:

When you run:

docker compose up

Compose:

• Builds or pulls image
• Creates container
• Connects to network
• Applies restart policy
• Starts container