A solder is usually made of a combination of tin and lead or tin and copper. Because lead is hazardous to health, copper is used more with higher concentrations of tin. Always remember to wash your hands after soldering.
There are five types of soldering irons: simple irons, cordless irons, temperature-controlled soldering irons, soldering stations and soldering tweezers. All of them are used for different soldering purposes, from soldering large things in metal chassis to small capacitors, diodes and resistors in a computer motherboard.
When soldering circuit boards, there is no need to use a lot of solder. Applying small amounts makes it easier to determine whether the connections are fitting or not. A good solder joint has a shiny look and a clean-looking tilt from the part to the board.