What is Confluence?
Confluence is a software product produced by a company called Atlassian. The product is in the category of 'enterprise wikis'. Think of it as an enterprise version of Wikipedia - but without the content, which the enterprise itself provides.
Why do enterprises use enterprise wikis? Many people in the enterprise in different locations need to develop, review, edit, comment upon and publish content for their organizations in a collaborative framework irrespective of their location, access platform (PC, mobile), operating system, time zone etc. The established free availability of web browsers (e.g. Firefox, IE, Chrome, Safari) and the underlying HTML technology means everyone can access enterprise wikis because they are based on ubiquitous Internet access and HTML. Other solutions like Microsoft Sharepoint achieve similar things but are proprietary, often leading to higher licensing costs and dependency on proprietary operating systems and environments.