SharePoint is easy to start learn and implement if any one know HTML concepts.
SharePoint's core functions are 1) store documents in a more effective format and 2) bring an organisation together.
Most of the organisations uses SharePoint for internal operations and require changes as per their requirements. So the demand is keep growing.
At high level SharePoint is a platform where one can create sites which will have predefined designed pages.
Most of the time developers will be working with customizing the existing SharePoint pages, developing workflows and search configuration. Either Client side scripting or server side coding will be required to interact with SharePoint database.
These are few of the SharePoint features: Workflows, Alerts, Storage, Collaborate by sharing the information with other users or colleagues, Content management and Search