Strings

Strings are categorized by core material. Aluminum and Chromium windings = bright sound, quick response, Silver windings = rich sound, slow response, Tungsten = good projection, clear tone, quick response
The thicker the gauge, the more tension required to tune it to pitch. More volume, more effort to get sound, may not fit in fine tuners. Thinner gauge requires less tension to tune to pitch, making them good for repaired or old instruments that can't tolerate high tension. Less effort to play, less volume produced. Most strings sold are medium.