An alphametic puzzle (also sometimes known as a cryptarithm) is a type of puzzle where words are put together into an arithmetic formula such that digits can be substituted for the letters to make the formula true. Here are two examples, the first being one of the simplest and the second being probably the best known alphametic puzzle:
I S E N D + B B + M O R E ----- --------- I L L M O N E Y
In the first, I = 1, B = 9, and L = 0.
Below are links to my three pages dealing with Alphametic puzzles.