A soldering iron is a hand tool used for soldering.
It supplies heat to melt solder so that it can flow into the joint between two workpieces.
A soldering iron has a heated metal tip and an insulated handle. Heating by passing an electric current (supplied through an electrical cord or battery cables) through a resistive heating element. Cordless irons housing combustion of gas stored in a small tank, often using a catalytic heater rather than a flame.
Present day people are not using Simple irons less commonly, in the past were simply a large copper bit on a handle, heated in a flame.
Soldering irons are most often used for installation, repairs, and limited production work in electronics assembly. High-volume production lines use other soldering methods.
Large irons may be useful for soldering joints in sheet metal objects. Less common uses include pyrography (burning designs into wood) and plastic welding.
It is of different types, like Simple iron
Temperature-controlled soldering iron
The best technique for soldering is simple, so repeat this mantra: Heat the metal, not the solder.
For example, you heat the metal of a component pin and the metal of a circuit board pad simultaneously, and then you touch the tip of the rosin-core solder to the pad or the pin, but not to the iron.
If you have sufficiently heated the two metals (the pad and the pin), they will heat the solder, which then flows quickly to both the pad and the component pin.