A container is a section in your hard-drive that contains specific processes and resources within the section itself.
How does an image relates to a container?
An image is basically a file-system snapshot and a startup command. It consists of one-or-more files.
When we create a container from the image, the Kernel will isolate certain resources just for the container.
When we tell the container to run a startup command, the file being executed in the command will be put as one of the running processes in the container, allowing it to utilise resources within the container through the Kernel.