Flash memory is non volatile.
That means that when the batteries are removed from the Palm, flash remembers what is in it. Dynamic RAM is volatile. Flash is good for things that don't change, like databases that you read from, but not write to after the DB is stored. RAM is more dynamic, and you can read and write to it on the fly, while you need a special copy program to move things into flash. The Palm IIIxe has 8mb of RAM plus 2mb of Flash built in.