You interact with a program through its user

The user interface, in the industrial design field of human-computer interaction, is the space where interactions between humans and machines occur. The goal of this interaction is to allow effective operation and control of the machine from the human end, whilst the machine simultaneously feeds back information that aids the operators' decision-making process. Examples of this broad concept of user interfaces include the interactive aspects of computer operating systems, hand tools, heavy machinery operator controls, and process controls. The design considerations applicable when creating user interfaces are related to or involve such disciplines as ergonomics and psychology.

Generally, the goal of user interface design is to produce a user interface which makes it easy, efficient, and enjoyable (user-friendly) to operate a machine in the way which produces the desired result. This generally means that the operator needs to provide minimal input to achieve the desired output, and also that the machine minimizes undesired outputs to the human.

User interface

Explanation:

The user interface is portal that enables a computer user pass commands through the software to the Computer.

Mostly developers of Softwares have been advised to always ensure that the User Interface is designed in such a way that their experience is not made difficult rather happier.

A poor User Interface can not only ruin a User's experience but also render the software irrelevant to the User.