Difference between Communities and Sites in Salesforce?

Hi Suraj,

Community Builder

It is an intuitive, convenient tool for customizing your community. Community Builder lets you create a community based on a preconfigured template, and then apply branding, edit pages, update your template, and publish changes all from one user-friendly interface.

You can use  Community Builder when you want to achieve:

• Use one of the self-service templates—Koa, Kokua, or Customer Service (Napili)—to easily create a responsive self-service community.
• Use the Aloha template to create a configurable App Launcher.
• Design pixel-perfect, branded pages.
• Create public pages that anyone can access, or add private pages that you can add as a tab within your community.
• Build and iterate quickly using drag-and-drop reusable page elements.
• Use ready-made forms to create web-to-lead forms or gather customer feedback.
• Create data-driven pages, such as product catalogs or other listings, using your organization’s data.
• Set a home page and set up multilingual support for your community in Site.com Studio, a Web content management system that provides extra configuration options. Site.com Studio is easily accessible from Community Management.

Force.com Sites
Suitable for developers with experience using Visualforce, Force.com Sites lets you build custom pages and Web applications by inheriting Force.com capabilities including analytics, workflow and approvals, and programmable logic. So if you are looking to create sites programmatically using Apex and APIs, Force.com Sites is the product for you. Here’s what you can achieve with Force.com:

• Create public, branded pages that anyone can access.
• Leverage Visualforce to create private pages that you can add as a tab within your community.
• Write your own controllers, or extensions to controllers, using Apex code.
• Create custom login or self-registration pages.
• Build dynamic web applications, such as an event management application.

For more information you can refer to https://help.salesforce.com/articleView?id=siteforce_vs_sites.htm&language=en_US&type=0

Hoping it may help you

Community Cloud is a social stage of the Salesforce.com that is intended to associate and encourage correspondence among an association's representatives, accomplices and clients

Whereas sites in Salesforce empowers you to make open sites and applications that are straightforwardly coordinated with your Salesforce association—without expecting clients to sign in with a username and secret key. You can freely uncover any data which has been put away in your association through a marked URL of your choice.