What is the benefit of using Docker on virtual machines and what is the difference?

Question

Software design

Good afternoon!
I am reading another article about Docker and I understand what a convenient system, but I have one question that haunts me: does it make sense to use Docker on top of a virtual environment?
Let's say I use one of the SaaS solutions: DigitalOcean, Amazon AWS, or another cloud solution. The architecture is as simple as three pennies: 1 instance - 1 task (hence: DBMS server, application server, cache server, etc.), each instance has a snapshot and in case of a crash, you can raise a full copy in a couple of minutes.
In the case of Docker, it turns out that I should have the same type of hosts that contain the same set of containers (DBMS container, application container, cache container, etc.) and which rummage around and work with each other. Those. in the context of the system it turns out almost the same.

Answer 1

Cutlets - separately, flies - separately.
DigitalOcean - a cloud only in banners. This is an ordinary (albeit good) hoster providing vps.
Docker is lightweight virtual machines. In fact, it is possible to make analogues of amazon ws on their machines - with a bunch of instances and their own nice buns.
I myself understand this rather mediocrely - I have already transferred my server to docker and dokku, plus we plan to gradually stop running everything on iron servers in the company, and keep all services in dockers.

Answer 2

An example of a bad, but problem-solving docker
is a teamviewer for nix, which is greedy for dependencies with libraries, every time I update the system, I solve the problem with dependencies (not for long, but problems arise).
To avoid problems, I install the teamviewer in the docker container, and use it from the container, updating the system, the teamviewer continues to work for me, since the necessary libraries remain in the container.
In fact, docker = chroot
But docker has advantages:
1) Versioning, you can make commits like in git
2) Convenience, to create a container, we just do the command docker run base: the desired container
3) A huge repository of ready-made containers with pre-installed programs (but I don't trust them)
4) the ability to control using cgroup