In general, usability refers to how well users can learn and use a product to achieve their goals and how satisfied they are with that process.
A key methodology for carrying out usability is called User-Centered Design.
What Does Usability Measure
Usability measures the quality of a user's experience when interacting with a product or system-whether a Web site, a software application, mobile technology, or any user-operated device.
It is important to realize that usability is not a single, one-dimensional property of a user interface. Usability is a combination of factors including:
- Ease of learning - How fast can a user who has never seen the user interface before learn it sufficiently well to accomplish basic tasks?
- Efficiency of use - Once an experienced user has learned to use the system, how fast can he or she accomplish tasks?
- Memorability - If a user has used the system before, can he or she remember enough to use it effectively the next time or does the user have to start over again learning everything?
- Error frequency and severity - How often do users make errors while using the system, how serious are these errors, and how do users recover from these errors?
- Subjective satisfaction - How much does the user like using the system?