An interface is usually a shared boundary across two or more separate components of a computer system. Interfaces in programming consist of the set of statements, functions options and other communicational instructions. With hardware equipment, the interface makes a physical connection so that two pieces of equipment can communicate or work together successfully.
A User Interface (UI) can consist of operating systems, as well as command and graphical display formats, that allow the user to communicate with the computer.
When working within the IT industry, it is beneficial to know how an interface works and how to resolve any issues which arise.