What is the role of the layer in the Docker container architecture and why is it needed?

In Docker, each image consists of multiple layers. Each layer is a set of changes added on top of the previous layer.

Role of a layer:

• Reusability: layers are cached and can be used by different images, saving space and speeding up build times.
• Simplified updates: when an image is changed, only the modified layers are rebuilt.
• Change isolation: each layer contains specific changes (e.g., installing packages, copying files).

Example: if the base layer contains the OS, and the next layer installs Node.js, then when the application changes, only the top layer is rebuilt, while the base remains unchanged.