(MB) or meg: Unit of measure equal to 1,048,576 bytes, or 2 to the 20th power, often rounded to one million bytes, mainly used to express storage capacity. The random access memory (RAM) of a computer is always stated in MB.
Megabytes are the measurement used for the amount of hard drive space available, used, required, etc. One megabyte is equal to one million bytes or one thousand kilobytes. One megabyte is small by today's typical file sizes. Hard drive sizes are commonly given in gigabytes, each of which is one thousand megabytes. Memory is also measured in megabytes.