Plan drive project strive to reduce almost all end uncertainty at the start of the project and gradually reduce means

[Kumar101]

Agile team accepts that it is not possible to reduce any uncertainty at the start of the project and as team progresses in the project and gains knowledge about the product, end uncertainty is gradually reduced while means uncertainty is also reduced as teams gains more knowledge of the process. Plan driven projects want to have almost complete details about the end state of the project at the start while the means, the process on how the product is build is gradually improved.

please explain this with more vivid example as iam not able to understand this explanation given in the question?

[seema.sonkiya]

Please post your questions in the right thread. I am moving this question in the PMI-ACP Queries and Tips section.

[seema.sonkiya]

When we are following plan driven approach. In this case, we have the situation where we can plan all project requirements in advance. Things in the project are almost predictable. There could be some assumptions in the project (but not much). These assumptions and other uncertainties brings few risks which are reduced when we move ahead in the project.
For example, you are developing a mobile app and as you developed similar mobile app you can predict its requirement very well. In this app, you are working with a new vendor. Since it is new, you have some risks. As you move ahead in the project, you started knowing vendor well, and risks identified from vendor side are getting reduced.