Soldering is a joining process used to join different types of metals together by melting solder. Solder is a metal alloy usually made of tin and lead which is melted using a hot iron. 

The iron is heated to temperatures above 600 degrees Fahrenheit which then cools to create a strong electrical bond.

Solder is a melting alloy. The solder alloy is made up of tin (67% -) and lead (33%), and this alloy has low melting point, so it is used for soaking or stitching. This process is called soldering.

Solder or solder is an alloy made of  Tin (67% -) and Lead (33.%). and this alloy has low melting point. To use it as a joining material, it is heated to this temperature (500-600 0C) and melted. 

This melts then solidifies and in the process joins the adjoining metals. This process is called soldering.