We have a Product Owner, a Product Goal, and a Product Backlog in Scrum. Why don’t we have a Product but an Increment?
The answer is both historical and essential.
Scrum started as an iterative and incremental approach for software product development.
OOPSLA 1995 Scrum Paper:
SCRUM is an enhancement of the commonly used iterative/incremental object-oriented development cycle.Scrum Guide May of 2009:
Sprints deliver an increment of the final product that is potentially releasable.
The differentiation between product and Increment is important as an Increment might become part of the product if it fulfils all the aspects needed for verification and validation.
In my opinion the biggest problem with the Increment terminology is based on the fact that word Increment is used both in singular (one) and plural (many) in all of the Scrum Guides.
Scrum Guide 2020:
An Increment is a concrete stepping stone toward the Product Goal. Each Increment is additive to all prior Increments and thoroughly verified, ensuring that all Increments work together. In order to provide value, the Increment must be usable.
Multiple Increments may be created within a Sprint. The sum of the Increments is presented at the Sprint Review thus supporting empiricism. However, an Increment may be delivered to stakeholders prior to the end of the Sprint.
Let's untangle the confusion with a simple metaphor.
Soap-Bubbles
Have you ever been to a children birthday party or a circus where there was a show with soap-bubbles. Keep the image of soap-bubbles in your mind.
The product (I'll explain product in a minute) which is already being used by your customers would be a large soap-bubble as shown in Figure 1.
During the Sprint Planning the Scrum team defined a valuable Sprint Goal, created the corresponding Sprint Backlog consisting of for example 8 Product Backlog items.
Scrum Guide 2020:
The moment a Product Backlog item meets the Definition of Done and Increment is born.
As shown in Figure 2, next to the existing Increment many smaller Increments are created during the Sprint.
Done implicitly includes that all acceptance criteria have been fulfilled (see my other blog [1]) as well that it works with the existing Increment. None of the previous functionality may be broken. Additionally, there might be other items you might need to address through your Definition of Done. Think regulations and governance.
Scrum Guide 2020:
An Increment is a concrete stepping stone toward the Product Goal. Each Increment is additive to all prior Increments and thoroughly verified, ensuring that all Increments work together.
Figure 3 visualises the moment the freshly created Increment is validated and verified with the existing Increment.
If one of the tests of the new small Increment would fail to fulfil any point of the Definition of Done it would not be integrated into the Increment.
Scrum Guide 2020:
If a Product Backlog item does not meet the Definition of Done, it cannot be released or even presented at the Sprint Review. Instead, it returns to the Product Backlog for future consideration.
Once the Definition of Done is fulfilled the new Increment gets absorbed into the existing Increment and thereby making it grow as shown in Figure 4.
Now you know why it is called Iterative and Incremental product development.
The moment the Increment is placed into the hands of a user, it becomes the product.
The Increment(s) are internal, the product is external in the hands of the users.
[1] https://www.scrum.org/resources/blog/product-owners-you-do-not-accept-work-sprint-review