One of the hottest topics since 2014/5.
A container provides:
It has no knowledge of proccesses running outside of its own environment.
No GUI and no WYSIWYG. They’re designed to run one and one thing only in the most nimble way possible. Normally one process maps to one container.
Docker: Is the “default” virtualization engine for running containers, it’s not the only one but it’s king of the hill.