Debian Memory Requirements
Each Debian release and architecture has it's own (minimum) RAM requirements, which mainly depends of the type of installation (Graphical Desktop...).
Gnome user can use Hardinfo (in Menu Applications/System Tools) to know the installed/available RAM.
free is the unix standard command to display amount of free and used memory in the system. For example :
$free total used free shared buffers cached Mem: 2067696 679244 1388452 0 111500 123236 -/+ buffers/cache: 444508 1623188 Swap: 998572 368976 629596
MTD (Memory Technology Device)
Memory Technology Device (MTD) Subsystem for Linux Design is a generic Linux subsystem for memory devices, especially Flash devices.
The aim of the system is to make it simple to provide a driver for new hardware, by providing a generic interface between the hardware drivers and the upper layers of the system.
Hardware drivers need to know nothing about the storage formats used, such as FTL, ?FFS2, etc., but will only need to provide simple routines for read, write and erase. Presentation of the device's contents to the user in an appropriate form will be handled by the upper layers of the system.
See also: http://www.linux-mtd.infradead.org
RamDisk - use RAM as a disk partition
NotEnoughRAM - using Debian on low memory systems
Swap - swap space (virtual memory) management