The Chatter is a chat functionality, which is almost universally pluggable in any screen form.
The Chatter component is central component of the broader ERP Social Interactions package, which includes functionality for close interaction with clients, partners, suppliers, fans, etc.
It allows interactions with internal and external users much like the social networks, just in a business aspect.
The Chatter is integrated in the Client Center and can be used by clients to chat directly with employees. The Chatter can be very useful for impromptu support, quick handling of delivery or paperwork problems, etc.
Chats are attached to objects
Each chat is related to an object in the system. In this sense, the Chatter can be used internally for taking notes or discussions for specific data objects like Sales Orders, Payment Orders, Invoices, etc.
Much like the social networks, the Chatter allows reactions like Like, Haha, Wow, Sad, etc. This can further enhance the discussion of ideas and proposals in informal manner.