What are `flash` and `storage` partitions used for?

Hi there, I have some questions regarding some partitions defined in partitions_espruino.csv.

I thought storage partition was used for the file system, but turns out the default address for E.flashFatFS() is 0x30000 instead of 0x360000. (Maybe because it's outdated?)
I also thought storage was the target of the upload destination Storage in the Web IDE, but turns out the target partitions for Storage, Flash, and Flash (always) in the Web IDE are all js_code partition.

Is there any difference between the flash and storage partitions?

Any help will be appreciated :)