Generally in the "Fastest Known Time" world, they define "unsupported" as without any external support; that is, other people helping. You may only make use of publicly available resources. So for example, you can fill your bottle at the spring by Garfield Shelter, but you can't buy a piece of blueberry bread at Galehead Hut.
However, suppose you want fill your water bottle at the Hut, where water is free: if you regard the AMC huts as a "commercial enterprise" then your effort isn't unsupported; but if the huts are a non-profit organization (and not commercial, like a gas station selling water bottles), then it would still be unsupported. I am not sure how they adjudicate use of this resource.
A cache falls under "self-supported" -- unsupported would have no cache; and supported would mean something like, others drop the cache for you.
I think that in addition to the rules of the website that lists these efforts, there is also the idea that the initial record-setter can determine some details (such as, particular trailheads). There is also the consensus of the community.
I'll copy in the entire text from the FastestKnownTime dot com website -- once independent, but now owned by Outside Inc.:
https://fastestknowntime.com/guidelines
Styles
There are three levels of support, called styles. Each route may have separate gender categories for these three styles, and FKT submissions must state which style was employed. While these three styles are different from each other, none is better than the others; do what works best for the route and you.
Unsupported
Unsupported means you truly have no external support of any kind. You must carry everything you need from start to finish except water from natural sources. Public taps along the trail are fine, but no water from any commercial source even if free. This naturally limits the length of an unsupported trip. Spectating pre-arranged by an athlete is supportive, and was classified as support starting February 4, 2021. All FKT classifications previous to this date remain unchanged. Phone and digital communication is not considered support, nor are spectators and support people at the start and finish. Using public restrooms is not considered support, though using it as extended sheltering would be. Charging digital devices or headlamps at public power sockets is acceptable for unsupported attempts.
To be unsupported, all equipment and gear must be carried from start to finish. Wrappers/Trash (not gear/clothing) may be properly discarded along the way. One may drop gear (such as a pack while summiting a peak) if one returns to it and brings it back to the finish on the same trip. Using a bike or kayak can be unsupported if the above condition is met, such as on an out-back route where a bike is ridden from the start, left temporarily, and ridden back to the finish. If a bike or any other gear is cached in advance or left along the way, the effort is not unsupported.
Self-Supported
Self-Supported means you may have as much support as you can manage or find along the way, but not from any thing or person just for you; any support you employ must be equally available to anyone else. This can include caching supplies in advance, purchasing supplies along the way, staying at motels, and finding or requesting food or water. Camping in a friend's yard would be supported, because it is not available to the public. Except at the start and finish, spectating pre-arranged by an athlete is considered support. Many long thru-hiking routes are done self-supported. To get a self-supported FKT you must also beat the fastest unsupported time.
Supported
Supported trips can have as much support as you can enlist, as long as you are entirely self-powered. This can range from one person accompanying you for part of the run, to an entire team that runs with you the whole distance giving you everything short of physical assistance. Whether it’s just once or continuously, any support at all means it’s a supported trip. On many routes, the supported style can enable the fastest trips due to the ability to carry less weight. To get a supported FKT you also have to also beat the fastest self-supported and unsupported times.
Groups and Teams
Groups of people can employ any of the three styles as long as they all travel and finish together; a team may share gear and still be unsupported. However, if one member drops out that means they paced the other members, so the finishers will automatically be supported. Speaking and traveling with strangers you encounter by chance does not count as support. Running with a dog is not considered support.
Motorized travel and Equipment
All FKTs are self-propelled, though variations of certain routes allow a motorized vehicle to link significant features or to cross water or other obstacles. Use of motorized transport can never be considered unsupported; if an athlete drives, e-bikes, hitchhikes, takes public transit, or uses rideshare apps for off-route logistics (or linking features where specified in certain variations), the effort can be self-supported. If someone you know drives you it will be supported. Certain routes have a strict ethic of exclusive foot travel for self-supported records, even for off-route logistics; when this is the case, it will be stated in the route description (e.g. the Pacific Crest Trail).
