Hardware inside your computer that retains memory on a short-term basis and stores information while you work. RAM is one of the things that make your computer run faster. It comes in 32-bit, 64-bit, 128-bit, 256-bit, and higher, and you can add additional "blocks" of RAM, depending on your computer.
Slang usage of this term often describes someone who does not possess the mental capacities required for the task at hand, as in, "I wouldn't ask him to do it, he's a little short on RAM."
Actual RAM comes in a variety of forms:
DRAM (Dynamic Random-Access Memory): A memory chip contained on such devices as video and sound cards.
DRAM (pronounced "D-ram") is dynamic in that the chip contains an electrical charge (as opposed to SRAM, described below). The electrical charge will eventually die out, so DRAM must refresh its memory regularly (which it does automatically from your CPU). The only reason you need to know about DRAM is that it is related to access time and video cards.
IRAM (Intelligent Random-Access Memory): In development by Dave Patterson, it's a chip design that defies conventional computing economics by combining a microprocessor and a memory chip on a single piece of silicon.
MRAM (Magnetic Random-Access Memory): Memory chips with an unmatched combination of instant-on capability, reduced power consumption, speed, and density.
SRAM (Static Random-Access Memory): Primarily used for caching, it is faster than DRAM since the chip holds its contents without refreshing from the CPU.
SDRAM (Synchronous DRAM): A new type of DRAM that can run at much higher clock speeds than conventional memory. SDRAM synchronizes itself with the CPU's bus and is capable of running at 100 MHz (about three times faster than conventional FPM RAM, and about twice as fast EDO DRAM and BEDO DRAM). So, SDRAM is replacing EDO DRAM in many newer computers, but future PCs are expected to have CPU buses running at 200 MHz or faster. SDRAM is not expected to support those high speeds, which is why new memory technologies, such as RDRAM and SLDRAM, are being developed.