Copper is a chemical element with symbol Cu (from the Latin word cuprum) and atomic number 29.
It is a ductile metal with very high thermal and electrical conductivity. The metal and its alloys have been used for thousands of years.
In the Roman era, copper was principally mined in Cyprus, hence the origin of the name of the metal as cyprium (metal of Cyprus), later shortened to cuprum.
This is a reel of 0.25mm diameter copper wire which weighs 125 grams. An application for this type of fine, uninsulated copper wire might include winding your own inductors, transformers or electromagnets.
Two important considerations with wires are the self-heating caused by the current (a factor of wire diameter) and the voltage drop caused by the resistance a factor of both diameter and length of wire).