Why containerization matters

Containers give everyone the same environment, so there are fewer setup headaches and "works on my machine" bugs. New teammates can run the app with one command, and the same image goes from development to production. They're lighter than virtual machines because they share the host's operating system.

Without containers:
- "Install Node 20, Postgres 16, set these 8 env vars..."
- Different versions on every machine
- Bugs that only happen in production

With containers:
- docker compose up
- Same versions everywhere
- Easy to scale: run more copies of the container