In the 2020 version of the Scrum Guide, the Developers as one of the accountabilities in Scrum is defined as set of people that are committed to creating any aspect of a usable increment each Sprint.
In the same version of the Scrum Guide, it is mentioned that the Scrum Team is accountable for creating a valuable, useful Increment every Sprint.
I have observed Usable, Valuable and Useful being used interchangeably when describing Increments within the context of Scrum and this is my attempt to document my understanding. Useful, Usable and Valuable should not be used interchangeably as they do NOT share the same meaning.
For a product to be useful, it must be usable; and for a product to be valuable, it must be useful.
Sam Adesoga
Usable
For a product, A usable product is one that is fit for use and there is a closely associated measure for Usability known as “Ease of Use”.
On a mobile phone, a browser can referred to be “Usable” because a user can minimise the browser using a gestures such as the swipe. If the browser is missing such a feature, then this could referred as a defect and in effect the browser is not usable. (Note: This is debatable, as a user could still browse but just not able to do anything else.)
The “Definition of Done” which is a commitment for an Increment should include statement that ensure that the Developers are able to produce a Usable Increment each Sprint.
Useful
Usefulness means to “find a use” for a feature or product. Referring to the example above for a mobile phone, minimising a window is the “Usability” allows a user to switch between multiple windows on their phone.
The usability part is “ability to minimise a browser” and this is useful for “switching between different browsers”.
I cannot imagine how a product can be useful without being usable, hence the reason I believe that for a product to be useful, it must be usable.
Valuable
There many facets to defining Value but for the purpose of the article, I would like to focus on Value from the point of view of a Customer. In the mobile browser example, the Value could be the ability to switch between multiple browser windows which in turn helps to increase efficiency and saves users’ time.
Lets consider another example - WhatsApp
Whatsapp is an instant messaging tool that we all use.
Whatsapp is usable because we can launch and use all the feature in the application.
It's usefulness come from the users ability to send text, audio and video to their contacts but the value could be that it helps users to stay connected to their loved ones.
Within the context of Scrum, Scrum Team and it's stakeholders should attempt to deliver a valuable increment consistently at the end of the each sprint.