The World Wide Web uses HTTP, short for Hyper Text Transfer Protocol. Hyper text refers to the language code of html. A German developer back in the 1991, developed a program called a Web Browser. This program displays graphics along with colored or stylized text for a "Web page" or window, which is hosted at a server on the Internet. When your computer request information from another computer (server) using this protocol, it will receive from the requested computer a file called index.html or default.html in which your computer will execute in a browser (program). Then your computer makes requests for other files based off the information in the index file. These are files that you embed into your e-mail or UseNet articles. Any file can be transmitted on the Internet, however SMTP and NNTP protocols require a little bit more of a trick and each one has its own limitations and advantages.
SMTP can't handle large files. As it will take tons of time to transmit a single file, because the e-mail must contain the whole encoded file. When attaching a file, the file is placed at the end of the message where it is encoded into ASCII format using the encoding scheme known as MIME. You never see this because most e-mail programs recognize this and separate the attachment from the text message before the reader sees the file in the encoded format.
With NNTP the file should be the part of the message that is posted or sent. No additional text should be posted in the message, or it may screw up the decoding of the file. NNTP still suffers the same large issue that takes time to download large files. However with NNTP, you can break these files down to a packet size limit and link them together. This is referred to as multi-part posting. Additionally, due to the fact the NNTP has no real encoding format (no standard), new ones can be created all the time. Meaning better and more efficient encoding/decoding protocols can be developed. yEnc encoding/decoding is the latest such format developed by Forte. This improves the chances of the program decoding the file if the multiply parts came in at different times. Giving the readers program a larger advantage of reorganize the file to decode it. However the readers program needs to understand this format and be able to process the task. Despite this little flaw, yEnc is becoming a very large popular encoding/decoding scheme and may become the standard that replaces Uu encoding/decoding.
FAQ answers attributed to Raymond E. Feist are copyright by Raymond E. Feist.
It should also be born in mind that the answer given was only applicable on the date written, and to a specific question. You may find further, similar questions, in the FAQ.