Docker : What is the fundamental difference between docker container and docker swarm ?

Question

There are multiple cases:
1. A number of containers have been launched in the same host. how these container communicate to each other
2. Out of "x" numbers of containers in the same host, I want to enable communication between two specific containers. How I can achieve this ?
3. Containers have been launched into different hosts machine and I want to enable communication between these containers. What are the options available ?

Answer 1

Docker Swarm is a separate product which you can use to cluster multiple Docker hosts. Prior to Docker version 1.12 it was the only native Docker option for clustering hosts, and it needed a lot of additional setup for distributed state, service discovery and security.
It is a native clustering for Docker. The best part is that it exposes standard Docker API meaning that any tool that you used to communicate with Docker (Docker CLI, Docker Compose, Dokku, Krane, and so on) can work equally well with Docker Swarm.

Docker container is an open source software development platform. Its main benefit is to package applications in “containers,” allowing them to be portable among any system running the Linux operating system (OS).
Container technology has been around for a while, but momentum and hype around Docker’s approach to containers has pushed this approach to the forefront in the last year. It is one form of container technology.