Computer storage and operating memory is organized around BITS. BITS stands for Binary digITS. A BIT can represent only the numbers Zero and One. However when several BITS are organized together as a unit they can represent a larger number. Computers work only with numbers. The convention developed over years is to cluster 8 bits into a group called a BYTE. a byte can represent numbers from zero to 256. Grouping several bytes in a cascading fashion can offer the computer (and user) binary information representing almost any number imaginable within the capability of the particular computer. In memory or storage, though all data is stored in the form of bytes. Since everything in computer math is done in base 2 math, the capacity of memory is given as the number of bytes that can be stored. A KILObyte is 1024 bytes (2^10), Kilo is normally the prefix for 1000, and gives an approximation of the actual number of bytes. Similarly, MEGA is about 1 million, and GIGA is one billion, so a gigabyte is approximately one Billion Bytes of memory storage. The actual number is somewhat higher due to the difference between decimal and binary math notation.
Gigabytes--1000 of which composes one terabyte--are a unit of electronic and/or RAM storage capacity, that are equivalent to 1024 megabytes, which are another standard unit of electronic capacity measurement. Megabytes, in turn, are composed composed of 1000 kilobytes, another unit. Each kilobyte is made of 1000 bytes; one byte refers to a 8 units of data, whether in existence or capability, measured from a single digit of binary code, or bits. (one bit equals the amount of data required to write 1 or 0 in binary).