The computer industry uses terms such as megabyte and gigabyte and corresponding abbreviations MB and GB as a measure of information, memory/storage capacity, or computer speed. Here is a list of the names and their numerical equivalents:
KB = Kilobyte (10001, a thousand bytes)
MB = Megabyte (10002, a million bytes)
GB = Gigabyte (10003, a billion bytes)
TB = Terabyte (10004, a trillion bytes)
PB = Petabyte (10005, a quadrillion bytes)
EB = Exabyte (10006, a quintillion bytes)
ZB = Zettabyte (10007, a sextillion bytes)
YB = Yottabyte (10008, a septillion bytes)
Hence, a "500 gigabyte" hard drive holds 500,000,000,000 (500 billion) bytes.
Note: The precise binary equivalent of all the above numbers is actually 1,024 rather than 1,000. Therefore, a Megabyte is actually 10242, or 1,048,576 bytes.