[Miami_Son]

ROM is where the main OS and any OEM files/apps are stored. Nothing can be deleted from there. Some mods (like Manila files) will overwrite certain files, but they don't get deleted, just made invisible. They continue to take up space in ROM, which is static. The only way to reduce it is to flash a smaller ROM. Storage Memory is the area of the device where new programs and files get written to. It is not in ROM. Anything in Storage Memory can be deleted and the space reclaimed. Some of the programs that come with the device from the factory are in there as are things like shortcuts and configuration files that need to be modified by the OS while in use. Unfortunately, the more Storage Memory you use, the less RAM will be available for running the device. That's why it is best to install any program that can be to a memory card. Program memory is your available RAM. This is where the OS and startup files/programs get copied to when you start the device. This is volatile and gets wiped out with each restart. This increases and decreases depending on how much stuff you have loading on startup, the mods you make to the shell (Sense customizations) and how many running programs you have at a given time. It is dynamic. Poorly written programs with memory leaks can cause it to fluctuate wildly during the day.