container
A sealed package of code and its dependencies so it runs the same everywhere, often used for back-end jobs.
Like a shipping container that holds everything a shipment needs so it travels safely and opens the same way anywhere. A software container bundles your code and the extra programs it needs, so it behaves the same on any computer or cloud server.
Containers matter when you run work on servers, such as background jobs, image processing, or scheduled tasks. You rent time on the cloud, which is someone else’s computers, and the container keeps your setup predictable.
In practice you write a small recipe file that lists what to include and how to start the app. A build turns that recipe into an image, which is the blueprint a server uses to start a running container. Services like Modal run these jobs for you.