Overall view of clustering process

i have an inquiry
does i have to use docker to make nodes in cluster i had use docker to intialize 3nodes in cluster named ehr
on the other hand i create local single node cluster called first what is the difference between those 2clusters
and how i coud connet

im confused between the two method even they are the same steps and when to use

Install Couchbase Server Using Docker | Couchbase Docs (d2hn797qrz68ed.cloudfront.net)


i had the steps but i need an over all answer about how to perform clustering process
does should i create multiple port number like 8091,9091