Where should i place my images in NetBeans Java web app?

I'm trying to make a web app to upload photos/images.

The NetBeans configurations confuse me in that it has both a web/ folder and a build/web folder.

Apparently, when the app is deployed, the latter is used for dynamic display; but when copying data is involved, the former is copied into first...

What is the difference between the two folders? Which one should i use?