EDIT Braille is an alphabet using a grid of dots to represent characters which are punched into the paper. These can be read by blind people using their fingertips gliding over them. The base grid consists of a system of 6 dots, although for computerbraille an 8-dot system is used.

 jsw 

EDIT History The Braille alphabet was created in 1825 by Louis Braille in Paris.
He became blind at three years old after he had had an accident in his father’s harness-making shop and at age ten attended a boarding school for blind children. There he met Captain Charles Barbier in 1821.

Barbier was a Captain in the French Army and had invented a system of dots punched into cardboard that allowed soldiers to communicate in the dark without being detected by the enemy. Barbier’s system used syllables instead of characters, used no punctuation and was based on 12 dots. Braille found this system very interesting since he and his fellow students had so far only been able to read by feeling the outlines of actual letters printed into paper, a method that was very slow and inaccurate because many lettershapes felt similar. He deemed Barbier\'s system too complicated, though, and modified it to 6 dots representing characters, thus creating an alphabet.

In 1825, at agte sixteen, Braille finished the Alphabet and it was adopted enthusiastically by the whole school. In 1839 Braille also created a system for musical notation.

Unfortunately, Braille never lived to see his system widely used. Only in 1850 the Braille-alphabet became the official alphabet in french schools for the blind and in 1880 it became standard for the schools in Europe. Today, it is international standard.

 jsw 

EDIT Basic grid of the Braille script is a 6-dot grid. They are positioned in three rows with two dots each and numbered from top to bottom, first the left, then the right side. These numbers are used to name the character, their Unicode-names are also just number combinations and not their relation to abc etc.
The grid creates 64 different possible dot-combinations including a blank.

 jsw 

EDIT 8 Point Computer Braille was created to make Braille compatible with computer systems. The traditional 6 point grid was extended by two extra points positioned below the 6 points (point 7 is below 3 and point 8 is below 6). It allows for a total of 256 positions and thus accomodates the whole range of ASCII-characters. In Germany, Computer Braille was standardized in 1992 with DIN 32982.

The advantage of Computer Braille is that its documents can immediately be translated on the computer into standard »black« type and vice versa. This is very useful in schools and other places where seeing and visually impared people are working on or with the same texts simultaneously. But the encoding of the characters is different from the traditional 6-point system, and texts written in one system can´t be transferred directly into the other. This usually means an institution (and anyone using either system) has to make a decision about which system to use, and students who for example switch schools can have real problems if they´ve only learned the other system.

 jsw 

EDIT Reading The dots are punched into paper and then read with the fingertips gliding along them. Usually, Braille is read with both hands simultaneously. While the index finger of the right hand is reading a line of Braille, the index finger of the left hand is already positioned on the beginning of the next line and starts with reading as soon as the preceding line is finished.

 jsw