What are conceptual and practical differences between containers (i.e. docker) and encapsulated packages (i.e. flatpack, snap)?

What are conceptual and practical differences between containers (i.e. docker) and encapsulated packages (i.e. flatpack, snap)?

docker deployment snapcraft flatpack

docker

Docker via snap - Cannot connect to the Docker daemon on a year old installation

docker ubuntu-18.04 snapcraft

docker

snap and gitlab-CI: error: cannot communicate with server: Post http://localhost/v2/snaps/hello-world

docker gitlab gitlab-ci snapcraft

docker

Enabling live restore on docker isn't keeping the containers alive

docker ubuntu service snapcraft docker-daemon

docker

How can I install Snapcraft in a docker image?

docker snapcraft

docker

How to create a Snap package that uses Docker to pull and run a Docker images?

docker snapcraft

docker