[thaanpaa]

Agile means delivering very small increments to users at a frequent pace, allowing them to provide feedback early and often. When done correctly, this eliminates a significant amount of guesswork. However, if the client (or, indeed, your own team or management) does not fully understand the process, things can go spectacularly wrong in many different ways.

[trickstra]

We still need to explain what "agile" is. Ask yourself why do we "need" to deliver small increments at frequent pace? Isn't it to be able to react to changes?

[thaanpaa]

I thought I said it. Its main purpose is to eliminate guesswork.

[trickstra]

It's main purpose is to react to changes, and make the whole process sustainable. It's literally one of the 4 main lines of the manifesto and the second of the 12 principles, and included in the meaning of the term "agile" itself, while guesswork isn't mentioned. But I can see how trying to predict what the markets will look like in 6 months involves a lot of guesswork, which is eliminated. I hope you can see that the only reason why guesswork is tricky is that there are a lot of changes in the meantime, so the ability to react to them is the deeper, actual main purpose.