Usability expresses the ease with which people can employ a particular tool or object in order to achieve a particular goal. Usability can also refer to the methods of measuring usability and the study of the principles behind an object’s perceived efficiency.
In human-computer interaction and computer science, usability usually refers to the efficiency or ease of learning with which the interaction with a computer program or a web site is designed.
Usability can be extended to multiple contexts such as consumer electronics, written instruction or mechanical objects.
Usability metrics are essentially:
