Depending on which newsgroups you subscribe to you may see a post which looks like it has been written in some obscure dialect instead of English. You have encountered an encrypted or encoded message.
The standard form of newsgroup encryption is called ROT13 which stands for "ROTate 13 characters". Every letter in the message is "rotated" 13 letters down the alphabet. A translates to N ; B translates to O and so on. The subject line of a ROT13 post remains in English so you can understand what the message is about.
All newsreader software includes a decryption or unscrambling feature to translate the jumble of a ROT13 message back into English.
Encoding is a more complex procedure used to post binary, images for example, as newsgroup articles. Each bit in the file is converted to an ASCII character through a process known as uuencoding which stands for Unix to Unix encoding. Most newsreaders can automatically decode binary file attachments into their original format.
If the file is too large to be carried in a single message, it will be split into several posts, all of which must be downloaded to decode the file.