What does Upper Memory Area mean

IBM reserved the uppermost region of the PC memory map for ROM, RAM on peripherals and memory-mapped input/output (I/O). This region is called the UMA and lies above Conventional memory, between 640 kB and the 1 MB maximum addressable limit of the original PC's 8088 CPU. For example, the monochrome video memory area runs from &B000 to &B7FF. However, even with video RAM, the ROM BIOS and I/O ports for expansion cards, much of this 384 kB of address space was unused - even when a 64 kB window was reserved for the Expanded Memory Specification "frame" address into which EMS RAM was bank-switched. For example, on most PCs, all or most of the area from &C800 to &EFFF is normally unused.

"Here are the various used ram memory we have in stock."
16mb EDO used Ram Memory	32mb EDO used Ram Memory	64mb EDO used Ram Memory
32mb Sdram used Ram Memory	64mb Sdram used Ram Memory	128mb Sdram used Ram Memory
256mb Sdram used Ram Memory	512mb Sdram used Ram Memory	1gig Sdram used Ram Memory
128mb DDR used Ram Memory	256mb DDR used Ram Memory	512mb DDR used Ram Memory
128mb Laptop used Ram Memory	256mb Laptop used Ram Memory	512mb Laptop used Ram Memory

Acer Memory	Apple Memory	Cisco Memory	Compaq Memory	Dell Memory	Fujitsu Memory	Gateway Memory
HP Memory	IBM Memory	Intel Memory	Sharp Memory	Sony Memory	Sun Memory	Toshiba Memory