A book published in 1981, called Nailing Jelly to a Tree, describes software as “nebulous and difficult to get a firm grip on.” That was true in 1981, and it is no less true four decades later. Software, whether it is an application you bought or one that you built yourself, remains hard to deploy, hard to manage, and hard to run.
Docker containers, and the OCI standard for containers and their runtimes, provide a way to get a grip on software. You can use containers to package an application in such a way that its deployment and runtime issues—how to expose it on a network, how to manage its use of storage and memory and I/O, how to control access permissions—are handled outside of the application itself, and in a way that is consistent across all “containerized” apps. You can run your container on any Linux- or Windows-compatible host that has a container runtime installed.
Containers offer many other benefits beyond encapsulation, isolation, portability, and control. Containers are small compared to virtual machines, measurable in megabytes versus gigabytes. They start instantly. They have their own built-in mechanisms for versioning and component reuse. They can be easily shared via directories like the public Docker Hub or a private repository.