Soldering is a process in which two or more components are joined together by melting a filler metal and applying it to the joint. The filler metal is the solder, and is available in many different alloys for different applications.
Soldering requires a soldering gun or pen, which are fitted with soldering irons. The iron is heated to the melting point of the solder, which is generally lower than the melting point of the components being joined to prevent damage.
Soldering stations provide the most versatility because they are equipped with a temperature control system. The iron can be heated or cooled to the correct temperature depending on the alloy used. As long as the solder is alloyed with the correct ratio of metals, the joint can cool rapidly without cracking, providing the best electrical connection.