Usability measures how well designed (from the users point of view) an interactive system is. An interactive system can be any product that provides an user interface: e.g. websites, software application, mobile phones or any user-operated devices.
Several factors affect the usability of a system:
- Ease of Learning: How fast can a user learn the systems relevant functions?
- Efficiency: How fast can a user solve tasks with the help of the system?
- Memorability: How easy is it to remember enough to use the system after a certain time period again.
- Error frequency: How often do errors occur? How easy is it to recover from them?
- Subjective Satisfaction: How much does the user like or dislike the system?