Emery cloth and non acid type flux
copper
The type of material used to connect the pieces. Solder is used on copper or brass. Brazing uses a copper alloy and is used on Iron based items. Same process in how it is done.
To join copper wires or pipes to each other.
You don't glue it, you sweat them. That is the term used for soldering them together.
It melts solder. Solder was originally a mix of lead and tin that was used to join copper to copper (pipes and wiring) It is in the shape of a pistol, but does not shoot anything.
Soldering can be used to make a reliable connection between two pieces of copper wire that is less likely to develop a fault than other ways of making the connection.
Copper is used because it is a good conductor of heat and thus more energy efficient. The solder melts at a temperature lower than copper and the soldering iron is controlled to only reach a high enough temperature to melt the solder. There are metals that are more efficient at conducting heat, But considering the melting point of copper, it high availability and relative cost. Copper is by far the obvious choice to use in a soldering iron.
Flux is used to keep metals from oxidizing. Solder will not bond well with copper-oxides which are formed when copper is exposed to high temperatures (ie a soldering iron) the flux prevents the oxidation. If you were to solder without flux the solder joint would be weak and possibly completely nonconductive.
tubing benders are the best used for
It is not a good idea to use copper pipe with natural gas as any sulphur compounds in the gas can cause an oxide to form in the copper pipe. Often copper is used with propane. In these instances, soft copper tubing is usually used with compression fittings. The tools required are, pipe cutter and 2 wrenches.
"Scrap" copper destined for recycling (i.e., water tube, gutters, etc.) may have solders that contain lead but new copper sheet, strip, etc. does not.
Soldering iron is used in heating the metal for soldering. If you want to learn more about soldering iron visit en.wikipedia.org/wiki/Soldering_iron.