Understand the three Docker concepts that commonly confuse beginners running local services.
The core idea
A container image packages an application and its dependencies. Port publishing connects a host port to a container port. Volumes persist or share data beyond the container lifecycle, while environment variables configure behavior at runtime.
A practical way to approach it
Read the image documentation, publish only the ports needed, mount a named volume for persistent local data, and pass non-secret configuration through environment variables. Use a .env file locally only if it is excluded from version control.
Try it in a small project
Run a database container with a named data volume, connect a small API through a mapped port, then restart the container and verify that the database data remains.
Common mistakes to avoid
A container filesystem is not a durable database backup. Do not expose admin ports publicly or commit secrets in Compose files.
Key takeaway
Keep the first version small, make your assumptions explicit, and verify the result with a repeatable test. For production use, check the current official documentation for the tools and versions you choose.