Computer Data
To help understand computers it is best to first learn about computer data. Computer data is information required by the computer to be able to operate. It is used to:

Run programs - This is the actual executable program data that the computer will execute to run the program such as Microsoft Word.
Store program or system configuration information.
Store information that the computer user needs such as text files or other files that are associated with the program the computer user is running. A common example of a program the computer user is running is the Microsoft Office suite of products which include Microsoft Word, Microsoft Excel, and others. These programs are also known as applications.
Data Structure
Computer data is in what is called binary format. This means that it is always a 0 or a 1. It only has these two states and must be in one of them.

There are several fundamental data units which include:

Bit - A data unit which must be in one of the two binary states described above. It is the smallest data unit that exists.
Byte - 8 bits of data which has a possible value from 0 to 255.
Word - Two bytes or 16 bits of data with a possible unsigned value from 0 to 16535.


Data transmission
Data transmission is the act of sending data from one place to another. Data is transmitted both inside and outside your computer. There are two fundamental methods of data transmission.

Serial - Data is sent on a single line and one bit is sent at at a time. This is similar to a line which one item must come one after another.
Parallel - Data is sent on more than one line at a time. This may be any number of bits at a time, but is usually one word at a time (two bytes) or possibly three bytes at a time.