The power of a computer is mainly determined by the speed and capacity (size) of each component.

Speed is measured in hertz (Hz) i.e. cycles per second (operation per second). Hertz is the unit of measurement for frequency.

Capacity is measured in bytes (B) where 1 byte = 8 bits (binary digits) = 1 character (i.e. the number of bits you need to encode 1 digital character). Byte is the unit of measurement of digital information. 

A binary digit (bit) is the basic unit of information. It can have only one of two values: 0 or 1. The two values can also be interpreted as logical values (true/false), algebraic signs (+/-), activation states (on/off).

Decimal system:

Kilobyte = 10^3 = 1.000 bytes

Megabyte = 10^6 = 1.000.000 bytes

Gigabyte = 10^9 = 1.000.000.000 bytes

Binary system:

Kibibyte (kilo binary byte) = 2^10 = 1.024 bytes

Mebibyte = 2^20 = 1.048.576 bytes

Gibibyte = 2^30 = 1.073.741.824 bytes