Docker - SWARM i am lost on this section

I am lost on this section

Are you saying that i need two different linux servers/instances to follow the demo. If so, do i need to install docker on all those three servers?

Please help

Demo -Docker Swarm

https://kodekloud.com/courses/296053/lectures/4554811

Yes you have to. Suppose you are deploying containers from master and other instances are seeking from docker service then how you will get containers on those instances.