Hi there,
it seems those phrases often cause confusion, I'll try to give a short definition (as far as I understood):

Multisegmented Downloading vs. Swarming
'Multisegmented Downloading' is what modern download manager and Gnutella clients do, download a file from multiple sources at the same time (increasing download speed). 'Swarming' means the same + spreading small file partials over the network automatically (increasing availability and download speed, distributing often requested files, balance load).

Most time people mean 'Multisegmented Downloading' if they talk about or 'Swarmed Downloads' or 'Swarming'! If you mean the real swarming better talk about 'Real Swarming'. To show you more about the difference: When we talk about downloading multisegmented the partials (file chunks) are typically very big, up to the full file size. Partials/chunks from Real Swarming are much smaller, a few 100KBs or whatever will fit best to the needs of making modem users part of the network. Segmented downloading and Swarming does NOT exclude each other! Swarming is just a bonus and actually not available on Gnutella these days. Real Swarming is far far future on Gnutella.

Swarmed Downloads or Parallel Downloads
People mean usually 'Multisegmented Downloads', those are only further synonyms... see above.

Partial upload
When a client does upload a file before it is finished with downloading the whole file itsef. This way especially big files get distributed faster and more often.

Automatic resume
When a client automatically downloads the full file and if a peer drop (or all) it full automatically searches more peers and continues the download without any further user interaction is needed. Automatic resume does need automatic requeries or other kind of techniques to find more peers offering the original file.

Feel free tor add more phrases & definitions below.... :-)

PS: Morgwen forced me to write this post, hehe. Here some older posts with more details:
"Improve Download Host/Speed" - http://www.gnutellaforums.com/showth...light=swarming
"A better way to promote sharing" - http://www.gnutellaforums.com/showth...&threadid=5939
"Thoughts about Segmented Downloading" - http://www.gnutellaforums.com/showth...&threadid=6396

A note from me (summary from the links above): The bandwith of modem users is completely wasted right now and modem users are often "forced" to be freeloader. Actually this egoizm is contraproductive and means less files for all. While high bandwith users can share the traditional way, swarming might be a key to make low bandwith users share with the network, without any significant negative effect or traffic-overhead. For both, for high and low bandwith users, sharing should mean there is a guaranteed high percentage of bandwith available for their own use! Conclusion, there are many ideas to envolve Gnutella and all work together. 1. A superpeer concept for dynamic traffic routing = reducing backbone traffic + improves network toplogy + increases horizon (more available files). 2. Search-caches for reducing double/multiple routed traffic = reducing high amout of search backbone traffic. 3. Swarming technology (as last step) = make use of the high amout of wasted bandwith + will spread often requested files + balance load + less "busy" servants (more available files). Please discuss about swarming and other possible improvements in the threads above and use this post for Gnutella definitions.