A Megabyte is a piece of data that contains 1,048,576 bytes of data. Usually a megabyte is thought of a 1,000,000 bytes of data instead of 1,048,576 bytes of data, this cnn lead to errors in calculating hard disk and floppy disk space. You will commonly come across megabytes when downloading large files like mp3 and mpeg files. Megabytes will be represented by MB on download windows.