A megabit (Mb) is a unit of information storage.
1 megabit = 106 = 1,000,000 bits (or 220 = 1,048,576 bits). Also 1/8 of a megabyte.
The megabit is most commonly used when referring to data transfer rates, and is the most common unit of measure for individual computer memory chips and some entire memory modules (such as video game cartridges).