where is the result of a www download stored?

Where is the result of a www download stored?
Say I use www to download a png or an assetBundle.

Does unity write it to one of the paths, or just store it in memory.
If just in memory how do I write it to a directory.

I believe it is only stored in memory. If you are downloading a png or assetBundle use the WWW.txt or WWW.bytes to get the data downloaded and create a file to dump the data into if you wish to store the results on disk.