The difference between Docker and Docker-Swarm is as follows:-
The purpose of designing Docker was to create an environment for running containers.
Whereas Docker Swarm runs on top of many Docker hosts to orchestrate containers on many machines. Docker Swarm also adds some capabilities to docker, like cross-machine docker networking, clustering, and simplify management on large container ecosystem. It can run on a single machine, but for study purposes.
Another difference is that Docker is one of the container technologies while Docker Swarm is a container scheduler similar to Kubernetes. If you are interested in learning Docker and Docker-swarm then I will suggest you must take up the following DevOps Training Course, this course comes with many advantages that will help you further in your life to grab your dream job, you get the job assistance, life-time course access with the life-time support and many more. If you are more into reading you must read the following DevOps Tutorial. I am mentioning the link of the video by which I came to know about these things. .