A packet is a collection (cluster) of information of a file that is traveling over the Internet. Packets size many be large or small, but most servers have a certain packet size limit. And if the packet is larger then the allotted size, the file is ignored and the server will never send the packet on to its next destination.
Since some servers have packet size limits, which vary widely. Many binary files (programs and multimedia) can be quite large when encoded. In order to handle this situation, UseNet provides that large articles can be broken into several pieces and linked together. We call these ‘multi-part posts'. It so happens that this break down of a file is actually equal to the size of a packet.
Now the problem is that packets can take different routes to get to your server since each packet is treated as a new file. Sometimes packets get deleted or never reach your server. What does this mean to me? You can't view a binary unless you have all the packets or parts of the post. So the larger the file, the more packets it has, and the more likely chance that the file will have missing parts.
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.