I am absolutely new at Salesforce.
Can anybody explain what is the difference between Salesforce communities and salesforce Chatter (if any)?
Chatter and Salesforce Community are two very different things. Chatter is for messaging while Salesforce Community is like a portal. Chatter is available inside of a Salesforce community.
According to Salesforce, Chatter is:
Chatter is a brand-new way to collaborate at work. Because status information about people and important projects is automatically pushed to you, Chatter makes it easy to connect with the people and information you care about most.
When thinking about Chatter, try to picture it as a replacement of email, instant messenger, and a bulletin board all at once. Your users can communicate with each other in groups, on their personal feed, on feeds on specific objects, over instant messenger, or even direct message.
According to Salesforce, Salesforce Community is:
Salesforce Communities is an online platform that enables rich collaboration between employees, customers, partners, suppliers and distributors. Organizations can create fully-branded public or private communities that connect members directly with each other – and with relevant content, data and business processes. Salesforce Communities is the only community platform that combines the power of social with mobile participation, trusted security, and direct connection to business processes.
When thinking about Salesforce Community, think about a portal. Salesforce Community is a way for your customers or partners to directly interact within your Salesforce organization. It has Chatter enabled, so your Community users can utilize that functionality.