Incremental delivery seeks to de-risk the approach by delivering small chunks of discrete value early and often to get feedback and reduce uncertainty. This allows us to determine sooner rather than later, whether we're building the right thing. 

As you can see from the following hypothetical risk profile, by delivering increments of ready-to-use working software, we reduce risk significantly after only 2 or 3 iterations:

This is combined with an approach to planning that allows us to quickly pivot or change direction based on new information.

With an adaptive plan, the focus is on prioritizing and planning for a fixed horizon, for example, the next three months. We then seek to re-plan once further information has been gathered. This allows us to be more flexible and ultimately deliver something that our customer is much more likely to need.

The following diagram shows that each iteration or increment in an adaptive planning approach allows an opportunity for a correction to the actual business needs: