Usually they are made out of copper or nylon. Usually for fingerpicking or beginners, it is pregerred to use nylon. For strumming or for advanced players they use copper. they usually use nylon for classical giutar: barok, romantic,...
He wanted a giutar that would sustain forever. In his words "you could strum its strings, go grab lunch, and when you returned they would still be ringing". He was the best player and one of the greatest inventors of this era.
Five Apex A banjo typically has four strings, and sometimes has a fifth string as well, which is plucked with the thumb. Also, there are special banjos with only three strings or as many as six strings.
Originally, the mandolin had 6 strings. Later designs included 8 strings (4 pairs) and the strings were plucked with a plucktrum. Other designs have multiples of 4 strings, up to a maximum of 16 strings.
Harps come in many sizes. A concert pedal harp (the kind used in orchestras) usually has 47 strings. Some student pedal harps have 40 strings. Large lever harps have 27 to 38 strings. Small harps have 19 to 26 strings.