Let's say you have a really small webpage, no more than 50K worth of material or so. You want it online, but you certainly don't want to set up a whole paid ISP account just for a paltry 50K worth of material. And maybe this is material which you're not going to update very often, if ever, such as the homepage for a mailing list. You're tempted to use a free webpage provider, but a number of those will delete your page if you don't update it often enough (eg.Angelfire) or at least deactivate it (eg. Geocities), and the fact of that matter is, even if ISPs don't understand this, you have a life outside of the Internet.
What do you do?
One answer is a simple concept called "subhosting". It's a purely informal arrangement, no money changing hands or anything else TOS violating like that. What you do is you find somebody you know who you feel is reasonably trustworthy. You give him the files that you'd like to put online, he creates a subdirectory, and puts those files in that subdirectory. That subdirectory becomes your page, courtesy of his donation of space. In informal terms, he becomes your webmaster, and your ISP, after a fashion, hence the name "subhosting".
Recently, Geocities took to deactivating sites which had not been updated for a while, a new practice for them, which caused a great deal of unahppiness. A few people find out that I plan on updating this site with some regularity, as it is the home of the Alternative Chicago/Ft.Wayne Burners' List. This makes me a natural candidate to do the subhosting thing, especially since I do plan on having space to spare. There is singularly little point to keeping old event announcements up, so material won't be accumulating. I see this as a "win-win" situation: the subhostees don't have to worry about deletion, and I get added hits on my site, from that link that says "this page is being subhosted on..."
Please be conscious of the fact that this is going on, and don't corner the author of a page subhosted in one subdirectory and ask him why he wrote something on somebody else's subhosted page in another subdirectory. Simple enough? My homepage lies ahead.