i know it's an excessive simplification, but basically the "useful" part of the strings is everything between the nut and the bridge. the string segments between the tuners and the nut can be used for some 0/1 bending effect - but for the rest are basically a potential source of rattles and unwanted vibrations.
here come the string dampeners - of course they can be used in various positions, but the most common is behind the nut.
every absorbing material can be used as a dampener. hair bands, strips of tissue or soft paper... but they're all temporary, ugly, not really effective and quite graceless solutions.
the gruvgear string dampeners fit perfectly (they come in 3 sizes but can be easily adapted anyway), are absolutely effective and are easy and fast to adjust.
the only downside is the price - but they're worth it.
