In most computer systems, a Byte is a unit of data that is eight binary digits long. In other words, a Byte has 8 bits. Byte is also commonly used to hold a character such as a letter, a number or a typographic symbol e.g. the letter "n", the number "6", the dollar sign "$" each needs one Byte of disk space to store. The byte is commonly donated by capital letter B ( small b is used to donate bit). Thus the terms kilobyte is represented as KB (approx a thousand Bytes - 2 to the 10th power or 1024 bytes in decimal notation), Megabyte or MB (approx a million bytes - 2 to the 20th power bytes, or 1,048,576 bytes in decimal notation.), Gigabyte or GB (approx a billion bytes - two to the 30th power, or 1,073,741,824 bytes in decimal notation.) etc.
To give you some physical idea of how much 1 GB disk space can hold, let me give you a simplified example. An average web page on the Internet is about 30 KB which is 30,720 bytes (30 x 1024). So with 1 GB disk space you can build a web site with approx. 35,000 (thirty five thousand) pages (1,073,741,824 divided by 30,720).