RAM (Random Access Memory): the PC’s primary storage area, used to write, store and retrieve information and program instructions which are then passed to the CPU for processing.. The type of RAM used affects performance as the information stored here has to be refreshed many times per second by the processor.  Manufacturers are continually coming up with new designs to provide the fastest possible access times at the lowest possible cost.

ROM (Read Only Memory):  Read Only Memory: an integrated circuit chip containing programs and data that can be accessed and read but cannot be modified.

Primary Cache: The primary cache (or 'level 1' cache) is based on the CPU and is a temporary storage of instructions and data organized in blocks of 32 bytes.

Secondary Cache: Most PCs are offered with a secondary cache to bridge the processor/memory performance gap. Secondary cache (also know as ‘external’ or ‘Level 2’ cache) uses the same control logic as primary cache.

DRAM: DRAM chips are large, rectangular arrays of memory cells with support logic that is used for reading and writing data in the arrays, and refresh circuitry to maintain the integrity of stored data.  . Memory arrays are arranged in rows and columns of memory cells called wordlines and bitlines, respectively. Each memory cell has a unique location or address defined by the intersection of a row and a column.

SDRAM:  SDRAM works quite differently from other memory types.  It exploits the fact that most PC memory accesses are sequential and is designed to fetch all the bits in a burst as fast as possible. With SDRAM an on-chip burst counter allows the column part of the address to be incremented very rapidly which helps speed up retrieval of information in sequential reads considerably.