It is mainly a qualitative method with the help of which you can test how easy a design is to use on a group of representative users, while the moderator observes closely the steps in completing some predefined tasks, to see where they encounter problems and experience confusion.
We do different types of usability testing:
Usability evaluation: testing of a new/updated service pre or post launch and in this case, it is important to see how intuitive, how easy and pleasant is the process for a new user. Usually, we done it to identify potential issues, things that slows the process and transforms it in a “not so good” user experience. In some cases, the evaluation can also be made in comparison with the main competitor’s site, in order to learn from other experiences as well.
Exploratory usability testing: we usually done it before finalizing the design of the product and its main objective is to identify those specific functionalities that users consider to be mandatory in order to meet their needs. In this case, moderator works with different hypothesis and scenarios for the new product ( in terms of functionalities, services, etc.) and its mission is to identify together with the respondents the unmet needs and their possible answers as base for the innovative process.