Clone "Customer Community Plus Login User" profile
Enable Communities in SF org.
Provide the unique URL
click on New community
Select a template
Give name and URL
Once community is created, click on Builder.
Click on components to add components.
Once you make necessary changes, click on publish.
For configuring users for community, Administration ==> Members ==> select appropriate profiles, permission sets.
For configuring login settings for community, Administration ==> "Login & Registration"
You can select a checkbox for allowing self registration for the user.
Click on Settings and Activate Community.
Community provides experience on top of what other SF products you have(Sales, Service, Marketing)
Internal users having SF licenses can access communities without purchasing additional licenses.
For external users need to purchase customer community, customer community plus, partner communities licenses based on need.
If you create a public community and want to give guest users unauthenticated access then no need for license for those guest users.
One external user license can login to multiple communities on same org using same license.
You can assign appropriate page variation to appropriate audience.
After you create a new page, add navigation menu and select the page created. So that user on click of navigation menu can go to the page.
Lightning Bolt makes it easy to export your customized community and use it to jump start new projects.
Using Branding Sets you can create personalized experience for different audience groups.
Using CMS Connect, you can reuse your existing html/javascript/css into SF.