Low% means finishing the game with as few items as possible. Or, in other words, skipping as many items as you can. This means that you sometimes have to go out of your way in order to skip one item. Naturally, that is slower and thus, low% takes longer than any% (which means beat the game as fast as possible, no restrictions). Compared to optimal any% with sail and quiver/light arrow skip, this route also skips obtaining the hero's sword. It is possible to skip more items in a TAS setting, namely the mirror shield and fully charged master sword (by unloading the Ganondorf Cutscene after setting up Actor Unloading with Hyxost Bombs), as well as the Deku Leaf and Magic (by hovering into Ganon's Tower, unloading lots of actors in Ganon's Tower and performing a leafless Puppet Ganon Skip), but this is currently the RTA limit.