There are six dots in a Braille cell. Each dot can be either raised or left blank. A black dot is raised on the paper so you can feel it (circles represent dots that have not been used). A quick calculation should tell you that there are $2^6$ possible arrangements of the six dots. However, some would be difficult to tell apart if you were blind and so no two letters use the same arrangements placed in slightly different positions, for example the letter "d" is represented in the following way: so no letter uses .