How many characters can one make with braille?

There are 64 six-dot characters that map to ASCII. Braille is a robust system that includes contractions of common words and letter combinations to save space.

You can learn more by googling “Braille character set” on your own, rather than asking on fluther.

6 dots can make 2^6 = 2×2x2×2x2×2=64 unique combinations.
You can double that by including or deleting a space between vertical 3 dot columns. That would not be standard but it is possible.