In Salesforce,a community helps the company to share information, connect with people of outside world
who are key to your business processes, all together in one place. We can easily communicate with internal users, portal users and external users through community.
Sometimes you need to create different communities for different purposes, so you can make multiple communities for an organization.
For example, you could create a customer support community to reduce support costs or you could have a community for an upcoming event.
You can use easy point-and-click branding tools with Lightning templates or go with the Visualforce pages to create branded collaboration spaces. You can easily customize your community to use your company branding or designing. Communities use Standard Salesforce functionality so you can share a subset of features and information from your internal Salesforce Org using Communities.