RAM is Random Access Memory. Pretty much you can write any data here. This is how pre-WM5/WM6 devices used to work. They install their programs in RAM. But starting from , WM5 changed the whole RAM concept , RAM is now well RAM...It will be 'Program Memory' , it will no longer serve as a 'Storage Memory'. Certainly , there is no more fight over Program/Storage. This is pretty much dedicated for Program Memory. Thats all..You can't do anything in here. Last time you could adjust to get more storage or more program memory but now its fixed

ROM , read-only memory. Pretty much like what callmepaper said , this where your 'OS' resides. Its also called as the 'Hard Storage Memory' (for WM5/WM6). Anything you install in 'Device' will be written to ROM. Thats why even after a battery drain. You still have your data there kicking. Smart eh ?. Before this , you could not do anything to ROM , on older devices..Extra ROM Space are often used as 'Storage Disk' aka iPaq Storage Media. But now its being utilised as 'Storage Memory'.

Storage card = nothing much to elaborate on

128MB ROM + 64MBMB ROM seems to be standard. Although there are 256MB ROM + 64MB RAM and even 1GB (Atom Life ?...Something like that). It does not matter. 128MB ROM is sufficient enough for your just about anyone