What components and technologies are involved inside a Docker container for its operation?

Docker containers utilize several key technologies and components for their operation:

• Namespaces — isolate container processes from host and other container processes. For example, PID namespace isolates process identifiers.
• Control Groups (cgroups) — limit and control resource usage (CPU, memory, disk) by the container.
• Union filesystems (OverlayFS, AUFS, etc.) — enable the creation of layered filesystems, where the container image consists of multiple layers, saving space and speeding up startup.
• Docker Engine — a daemon that manages containers, images, and interacts with the OS kernel.

Inside the container, an isolated process runs, which sees its own filesystem, network, and processes as if it were running on a separate machine, but it uses the host OS kernel.