• (flashing the) FIASCO aka *COMBINED*, also referred to as "rootfs" though this file and flashing process also consists of / affects NOLO bootloader (the several stages), the kernel, and usually the GSM modem firmware, in addition to the root filesystem which is basically the content of your 240 MB NAND flash storage and implements the Linux operating system.
• (flashing the) eMMC aka *VANILLA*, which will replace the complete content of N900's internal 32 GB eMMC storage (embedded MMC), which is: the /home partition which has your stored browser passwords and game highscores and calendar and contacts etc. /home is also containing /opt. Plus eMMC stores all the content of the MyDocs 28 GB VFAT partition, where all the media and docs and other user content lives.