The program snow is used to conceal messages in ASCII text by appending whitespace to the end of lines. Because spaces and tabs are generally not visible in text viewers, the message is effectively hidden from casual observers. And if the built-in encryption is used, the message cannot be read even if it is detected.
Snow exploits the steganographic nature of whitespace. Locating trailing whitespace in text is like finding a polar bear in a snowstorm (which, by the way, explains the logo). And it uses the ICE encryption algorithm, so the name is thematically consistent.